Our Testimonials

My 11 year old daughter has been playing softball since she was 6 years old. Last year proved difficult for her as her batting average fell significantly, she just couldn’t hit the ball. Every tournament I saw her confidence at the plate slip and the love of the game start to fade. As the tournament season came to an end I contacted Slammers to see if they offered hitting lessons for softball and that’s when we were introduced to Danny Sheridan. She’s seen him for just under 10 lessons and the comments from her coaches have been nothing but positive, the true test would be our opening tournament. 

This past weekend was our first tournament of the season and with the help of my daughter’s single, 3 doubles, 2 triples, and 4 RBIs, her team took home 1st place. Her batting average for the weekend was .600! 

To say I highly recommend Slammers and Danny Sheridan is an understatement. I have one happy softball player (her coaches and parents are pretty happy too). 

Jamie Lynn Cook

To whom it may concern,
Billy Cassidy has been my pitching coach since I was nine years old. My pitching wouldn’t be anywhere near where it is today without the help of Billy, and because of him I now pitch for Lakewood High School. I work with Billy for a few months prior to each season , and he is always available for mid-season tune up sessions.

Nowadays I average one strikeout per inning and consistently have a low era. Billy has taught me the proper way to train and gain arm strength. Because of this training my typical start is 5 -7 innings. Throughout the years working with Billy, I have been taught the fundamentals and finer points of pitching by a man who is a great coach, teacher and friend.

Jordan Rasser

To potential students of Billy Cassidy

We have worked with Billy Cassidy at Slammers off and on for five years. He has helped our three sons, not only on their batting and pitching, but also with their self esteem and self perception. Billy knows how to key in on each of our sons and their different quirks. He has a keen sense of what they are struggling with, whether it be a mental problem or a mechanical one. He is an excellent instructor who has helped all three of our boys tremendously. We can’t say enough about Billy Cassidy.

J. and Julie Fox

Slammers is the best thing that ever happened for our son to further his baseball career! Our son was dissatified with his high school baseball program for several years. After scouring the Internet for baseball alternatives, I discovered Slammers and scheduled some pitching lessons with Mark Holzemer. Mark improved our son’s pitching skills, and more importantly, restored our son’s confidence. Our son enjoyed and looked forward to working with Mark. One thing led to another, and our son ended up playing fall ball on the Slammers Select exhibition team.

This exhibition team played in many national tournaments and Junior Colleges from the Western United States. This exposure resulted in numerous offers from various colleges about our son’s availability. Our son is once again playing with the Slammers Connie Mack team during the summer of 2006 and will continue playing this fall in college. If you think your son may have what it takes to play college ball, I highly recommend the Slammers program. The coaching staff and level of instruction is outstanding and the college exposure he’ll receive far surpasses what any high school programs can provide.

Kay Dresler

To Slammers and whomever it may concern,

I don’t know how to begin to express my gratitude and appreciation for everyone associated with Slammers. My son, Christian, began going to slammers when he was just a small boy. At the age of 10, he began taking pitching lessons from Darryl Akerfelds during the winter. Darryl taught Christian the fundamentals of pitching and Christian was able to use this knowledge to his advantage. Several shutout games, 15 strikeouts in 6 innings for a couple of games and a confidence that was truly remarkable, were just a few of the results that were obvious. When Darryl moved, Christian hooked up with Clint Zavaras as his new coach and friend. Clint has taken Christian far beyond anyone’s expectations, and has given him a completely different attitude towards the game. He has even gotten Christian to open up and lose some of his shyness.

I cannot even begin to express my gratitude to Clint for the fine son and baseball player that he has given me. All the while Christian was playing Junior Baseball, I was the acting pitching coach. During Christians lessons, Clint taught me how to be a pitching coach too. Even though Clint was always Christian’s main coach, Mark Holzemer, Billy Cassidy, Darryl Milne, and Billy Martin have helped Christian when they could. Billy Martin has worked with Christian on his hitting recently and Christian has become an outstanding hitter.

When Christian made the Slammer’s Select team, all of the coaches and assistants worked with Christian and his abilities have improved beyond belief. My entire family feels like Slammers and it’s staff are all part of our family. We are always treated with respect and friendship. Any time I need something, all I have to do is ask and the staff are always there. Special thanks to Robbie, who has always helped us out. I’m sure I could go on and on with my appreciation, and believe me it would not be hard, but there is not enough space to truly thank the people at Slammers. All I can say is thank you, one and all, and especially Clint and Billy Martin. I truly believe that your coaching will allow Christian to go to the next levels if he continues to receive your help.

Al Nelson

Slammers Staff:

I wanted to thank the entire Slammers staff for all they have done in aiding in AJ’s development and in providing a very positive baseball experience during the past two plus years of Fall Select and Summer Connie Mack ball.

All the coaches we have been associated with (Billy M, Mark, Billy C, Clint, Darryl, Josh and Zane) are not only very good teachers and coaches, but quality people who I know AJ and his teammates all loved playing for.

The fact you have had two Summer Connie Mack teams not only make, but compete very well in both the past two State Tournaments speaks volumes for your program. The positive coaching styles your staff exhibits also created for good chemistry on all the Slammers teams AJ has played on.

As AJ moves on to continue his baseball career at Texas Tech, I am ever so thankful we were introduced to the Slammers Program. Keep up the great work and thanks again for this great experience.

Yours in Baseball,

Jeff Schugel

Major League Scout, LA Angels

I wanted to say a few good words about Slammers and Billy Cassidy. My son Nathan has been going to Billy for over 6 years now, since he was nine years old.

There is a reason my son continues to go to Slammers and to Billy, and to sum it up in one word ” RESULTS”. Every time my son needs tweaking with his mechanics, either with hitting or pitching, “DR” Billy Cassidy brings to the table a professional baseball background and teaches and talks from personal experience. I can only say positive and good things about Billy and the professional staff at Slammers…If you want your son to improve their baseball skills, I would highly recommend that you talk to Billy Cassidy and the Slammers staff.

Charles Fishel

Hi Billy C,

I wanted to thank you for all the work you put in with Dylan this fall. He and I truly enjoyed and appreciate all your time and energy. Tryouts went very well for Dylan. He is so excited about his tryout. ….He is really happy with his performance and the team he landed on. His team is going to Cooperstown which has been a dream of his for years. Words cannot express howe much your help is appreciated. Sincerely,

Dan Perko


First of all, I wanted to thank you for giving Andrew the opportunity to play for you. Andrew had a great experience and is looking forward to playing for Slammers Select in the Fall. Andrew was telling us at the state tournament all the players were talking and decided that this team was the best baseball experience of their lives. After the last game half the players were crying because it had come to an end. That says alot about the comraderie and respect they had for each other and the coaches.

This team played above all expectations. We believe it was due to the coaches. We can’t thank them enough for giving Andrew back his baseball career. The ” Billy’s ” ( Billy Cassidy and Billy Martin ) are a great coaching tandem. Every kid on the team loved and respected them. It was obvious when you watched them play. Their play reflected it. I believe what you are trying to do at Slammers to improve baseball in Colorado is on the right track. We came from California and Slammers is the closest thing to real baseball we have experienced since. Again, we would like to thank Slammers and the ” Billy’s ” for a memorable summer season. Sincerely,

Kapple Family

Hi Billy,

Cassidy Wanted to pass along some good news on your pupil. Travis pitched 3 innings yesterday, facing 14 batters, giving up 2bb and 3k’s. My pleasure was watching him keep his composure and confidence when a batter reached base.

Your teaching was very evident and we wanted to say thanks. We definitely want to continue his pitching lessons with you when you have some availability.

Thanks again,

Travis and Mike

To Potential Slammers Patrons,

It is with great pleasure that we are writing to tell you about our experience with Matt’s pitching coach, Billy Cassidy. In 2000 Matt was playing for the Wheatridge Blue Devils in Jefferson County. He was a good first basemen, but wanted to pitch. Unfortunately, playing first base exclusively for the previous five years did not provide the kind of experience that develops good pitching skills and we feared he might injure his arm.

Fortunately for us, Billy Cassidy had just begun to provide pitching lessons at Slammers. Billy’s patient coaching style fit Matt perfectly. That summer Matt pitched with Billy every-other week and his skills improved tremendously. Matt has continued to pitch routinely at Slammers under Billy’s supervision and the watchful eye of a many other good Slammers coaches. He has been on the Mullen High School varsity baseball team the past two years averaging more than one strikeout per inning and this year leading the team with wins. This summer he is happy for the chance to play on the Slammers Blue team. He is looking forward to his senior year and is already catching the eye of college coaches. As parents, we have greatly enjoyed watching Matt pitch and enjoy the game.

Thanks Billy!

Matt’s parents,

Mark and Pat Gemperline

Potential Slammers Customers and Players,

I was looking for some pitching lessons for my son about 4 years ago, he was 12 at the time, and I knew Slammers had a good reputation. While my son was in the Winter Hitting League at Slammers, I asked about instruction and Billy Cassidy was presented as a good choice. I had my son throw with Billy one day during the course of the league, and asked his opinion afterwards. Billy, true to his nature, gave me an honest assessment of my boy’s skills. Live arm, but he needed alotof work on his mechanics.

Well, Billy got my son’s mechanics in shape, and the following summer he threw his first no-hitter. His fastball topping out at about 60 mph. Needless to say I was thrilled and called Billy right away to thank him. Billy, always humble, shrugged it off and said that my boy did all the work. That is a prime example of how Billy treats the kids he works with. Four years later my son still seeks out Billy Cassidy exclusively for lessons. I have never heard Billy scream or shout to get a point across. He enjoys his work with the youngsters and he presents his ideas and assessments candidlly and respectfully. Billy’s love for his work shows through his respect for all who enter through Slammer’s doors. In return, he gains the respect of the players he teaches.

My son’s fastball now reaches 82 mph with, as Billy puts it “more in there “. Billy has been instrumental in my son’s development as a pitcher. He always has a plan for the next stage of development and his recommendations have been right on target. Working with Billy is a pleasure and I look forward to many more years of his instruction and guidance.

Thanks Billy, You are truly the best !!

Bruce Kostival

To Whom it may Concern,

I have been going to Slammers ever since I was eight years old. Baseball has always been my favorite sport and from the beginning, I have enjoyed the facilities and coaching that Slammers provides. I started out as a level 3 player in the South Jeffco little league program, so needless to say, until high school I never took baseball very seriously. It was just a game that I enjoyed playing but never expected to go anywhere. When I started to work more extensively with coaches Darryl Milne, Mark Holzemer, and Clint Zavaras, I developed a real passion for pitching. Their knowledge, experience and encouragement helped me realize I had a future beyond high school baseball.

Between my sophomore and junior year, I participated in the Arm Velocity program put on by the coaches and strength trainer, Zane Bendig. As I played summer ball with Columbine High School, I was at Slammers everyday for workouts with Zane. What an incredible program! My fastball went from 81 to 89 and I even touched 91 by the end of the summer. I played on the Slammers Select fall Blue team my junior year and the Black team the fall of my senior year. We took trips all around the country including the National Perfect Game Showcase in Florida, the senior fall showcase in Arizona, and we traveled around the region playing against junior and community colleges. It was one of the greatest experiences of my life.

The visibility and connections with the college programs and professional scouts is amazing. In November of my senior year I signed with the Division I program, Wichita State University. I continued to progress through the winter participating in the strength program and by the spring season I was really ready to play. I had one of the best seasons any pitcher could have. The Columbine Rebels won the state tournament. I received numerous awards, including High School All American, Colorado’s Gatorade Player of the Year, Male Athlete of Jefferson County, 5A Pitcher of the Year and MVP of the State Tournament.

Throughout the season I had been meeting with many professional scouts and by June I was projected to be drafted in the top ten rounds. On June 6th I was selected by the Milwaukee Brewers in the 4th round (#122 overall). I had never been so excited in my life. I signed a week later and now I find myself playing professional baseball and I love every minute of it. I believe that Slammers has been the biggest reason for my success.

With their wisdom, expertise, major league experience and encouragement, the Slammers staff can have a tremendous impact on baseball players of all abilities. It is a fantastic facility run by people who have a true love of the game. Through their wealth of knowledge and years of experience, they have created a positive environment where even a little league level 3 players can become a professional baseball player.


Evan Anundsen

P.S. I will continue to do all my off season training at Slammers!!

To whom it may concern,

When we moved our family from South Florida to Evergreen Colorado three years ago, we were worried about several things. One was being finding a reputable baseball instructor for our son Chase, who was nine years old at the time. We came across Slammers baseball in Lakewood Colorado, and met Mark Holzemer. Right away we were impressed with Marks credentials and his attitude towards the game. Our son connected with Mark immediately.

He made Chase feel confident about his abilities, and helped him to understand and correct his weaknesses without making him feel disheartened. As parents, Mark explains to us in detail about our sons technique. What he wants us to watch for and how to correct a problem if one should happen to arise. Chase is now twelve years old. He is calm, self-assured and dignified when he plays the game of baseball. He remains to be the lead off batter and closing pitcher.


Mike & Cheryl Haggard

To whom it may concern,

I just wanted to let you know how much you and all of Slammers have meant to us as a “baseball family”. We’ve been coming to Slammers for the six years that we have lived here. Coming from Florida where baseball is year round we needed a place for our sons to feel comfortable and happy while continuing to work on their baseball skills. We came to Slammers the first week we were here and felt right at home. The facility wasn’t the size it is now, but we knew right away the instructors knew their stuff and took pride in their ability to teach kids. You can have all the knowledge in the world, but if you can’t get it across,as a teacher and motivator it’s wasted.

Your instructors combine knowing the game with an ability to relate with kids and the patience to make it work. Our relationship with you as an owner and coach has been a pleasure. While it is a business, you run it with fairness and understanding. You can see that we all love our kids and want the best for them. As a coach you have brought Dillon and Cody a long way as baseball players.They have improved with your help and never see the lessons as anything but fun ,hard work and helpful. We appreciate what you’ve done for the boys and the friendship we have developed over the years. We intend to continue making Slammers our “second home”.

Sincerely, –

David Jess

Greetings Billy C.

Thanks again for all your help in the past with Matt. So far he has managed 4 wins and 1 loss. He has averaged over 1k an inning for the season ! He is excited to attend the UCONN camp this July. Thank you for the recommendation. We will get him in with you for preparation. He was also invited to Prescott Az for a pitching showcase in a couple of weeks…..

Thanks Again

Mark G.

Billy Cassidy,

My name is Renate. Conrad’s mother. I would like to take the time to thank you for the instruction you have given my son. He is receptive to your teaching and seems willing to learn the fundamentals of pitching and hitting. Last night I told him you went to UNC and he immediately said “Oh I am going there !”

We are grateful for your time…

Renate Rivelli

Coach Cassidy, I want to thank you for helping Michael this past Fall/Winter. You had a direct influence on Coach Pierce. They picked him without ever getting a good look at him. You also taught him how to hit with more power. He is hitting at least one out per practice at Metro.. He is really happy at Metro State… Thanks again,
John Coffey

Billy Cassidy

FYI, after Jordan pitched 1/2 a game on Wed in relief he got his 3rd start on Sat against league leading Dakota Ridge. Jordan had the most magical day of pitching in his life… Jordan pitched through the 7th, 1earned run, 1 walk and 7 strikeouts… Jordan was on top of his game and on top of the world. You would have been proud to say you are his pitching his coach. Thank you for all your care and effort you’ve put in over the years. It all paid off on that special Saturday.

Sincerely –

Mike R

Dear Billy C.

My son Travis had the pleasure to play on your Slammers Blue Baseball team this past summer. Not only did he enjoy the opportunity, but mostly he enjoyed your style of coaching. You might say he enjoyed ” Billy Ball ” especially when you have two coaches named Billy. I sincerely appreciated your confidence in his abilities, and I also appreciated the manner in which you treated each one of your ball players…. Thanks Billy !

Ralph Cruz