Inspiring lives on and off the court.

​Michael Esz

Director of Junior Programming & Development

Michael brings 23 years of professional coaching experience to GPTL.  He is currently certified with the PTR, USPTA, 10 and Under, and USTA Level 1 sports science commission.  In addition, he has been selected to the USTA High Performance program.  Michael is the former Head Pro and Director of Junior Development at Frog Hollow Racquet Club where he has extensively developed the junior program and the area’s top level players for the past nine years.  He was also a USTA National Zonals coach, National Nike Junior Tour coach for Middle States, and has coached numerous players that have received Division I college scholarships.  Michael is also an Early Developmental Coach (EDC) for the USTA Middle States where five of his students were selected to train with team Middle States.

​Email: michael@gptltennis.com

​Greg Williams

Director of Adult Programming

​Greg has over 25 years of tennis coaching experience in professional, collegiate, recreational, country clubs, sports clubs, non-profit organizations, adult and juniors of all levels.  Greg played in the Bill Johnson tennis program growing up in Philadelphia.  Greg formerly was the Director of Community Programming at Legacy Youth Tennis and Education.  He managed and supervised 45 NJTL sites and 24 After School Program sites in Philadelphia. Greg was a USTA High Performance National Coach, USTA Area Training Center-Player Development Head Coach, trained and coached one of his professional players at the US Open tennis tournament and was an Arthur Ashe Youth Tennis Center/Travel Team Coach.  Greg earned a USTA National Junior Ranking in the Top 30 in the U.S., American Tennis Association (ATA) ranked #1, 3 time NCAA All American in singles and doubles.  Greg graduated from Hampton University and was a scholarship player.  He has his PTR and USPTA certifications. 

​Email: greg@gptltennis.com 

Mark Kauffman

Mark Kauffman has over 20 years of tennis playing experience and several years of instructional experience with youth tennis programs.  He was an instructor at summer tennis camps in Lancaster where he developed various lesson plans for children of all skill levels.  Mark played competitively as a junior in the USTA Middle States Central Pennsylvania region where he held a top ten ranking and was the number one player and captain of his high school tennis team.  Mark is a graduate of Loyola University Maryland.

Andrew Wilson

Andrew Wilson has PTR Certifications for 11 to 17 and 10 and Under Tennis.  He has coached for Greater Pottstown Tennis since 2010.  Andrew is a graduate of Lebanon Valley College where he played four years of Division III Men's Varsity tennis and was a MAC Academic Honor Roll recipient.  He has competed in USTA sanctioned junior and adult tournaments and was MVP for the Boyertown Area Senior High School Varsity tennis team during his senior year.

Maryellen Wilson

Administrative Manager

Maryellen Wilson has PTR Certifications for Adult Development and 10 and Under Tennis.  Maryellen has over 40 years of tennis playing experience.  As Administrative Manager, she manages program registrations, communications, website content and Leagues organization.  Maryellen is a graduate of the University of Delaware and played four years of Division I Varsity tennis for the Blue Hens earning MVP honors.  For several years, Maryellen coached the Pottsgrove High School Boys' and Girls' tennis teams.

Email: maryellen@gptltennis.com


Chris Herdelin

Head Pro & Quantitative Analyst

Chris Herdelin, GPTL's Head Pro has been appointed to a new position as Quantitative Analyst funded by USTA Foundation.  Chris will foster improvements in tennis, education, health, and fitness using data to track and evaluate individual performance and offer suggestions for increased productivity and overall growth and development.  He has a Bachelor of Arts in Economics from Thomas Edison State University, Bachelor of Arts in History from Eastern University and is currently a Graduate Student at Texas A&M University working on his Masters of Science in Financial Economics.  Chris has been part of GPTL from 2010 mentoring all year-round tennis programs and has an extensive tennis background.  Chris was a Director of High Performance at the Arthur Ashe Youth Tennis Center in Philadelphia, where programs focus on exposing disadvantaged youth to lifetime tennis play.  Chris’ focus for GPTL will include surveying customer experiences, optimizing pricing, grant research and submissions, analyzing economic parameters, tracking performance metrics and applying data to implement mission focused strategies and to build partnerships.  For the after-school program, he will evaluate the performance of the participants and design the curriculum with a focus on health, fitness, education and tennis.

​Email: chris@gptltennis.com

​Kerriann Herdelin

Executive Director

Kerriann Herdelin is PTR Certified and has been teaching tennis for over 20 years with an emphasis on pre-teen youth.  She is an early expert in 10 and Under Tennis.  Kerriann is primarily responsible for grant writing and scheduling, planning, and administering all tennis programs.  Kerriann is a graduate of Niagara University with a Bachelor's degree in Elementary Education and was a Division I scholarship tennis player.  She was awarded a Master's degree in Special Education and is currently working on her Principal Certification.  For several years, Kerriann was the Head Coach of the Girls' Varsity tennis team at the Hill School. 

Email: kerriann@gptltennis.com