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Meet the Team That Keeps the Cardinals Healthy


Mercy Official Medical Provider of the St. Louis Cardinals

Mercy medical experts are with the St. Louis Cardinals all the way from pre-season to post-season. Their same pro-level care is on deck for you, whether you’re a little leaguer, a veteran, or somewhere in between.

Highlights from the Cards’ Care Team

Meet the St. Louis Orthopedic & Sports Medicine Team

Dr. Nicholas Greiner is in his first year with the St. Louis Cardinals medical staff serving as a team physician.


Dr. Greiner earned his medical degree from Kirksville College of Osteopathic Medicine and completed a Family Medicine residency at the University of Missouri-Columbia. He completed a Primary Care Sports Medicine fellowship at Saint Louis University. He has a certificate of added qualification in Sports Medicine.


Dr. Greiner is in his eighth year of practice, and beginning his third year with Mercy Sports Medicine. He has served as a team physician for the University of Missouri-St. Louis for the past six years and was the head team physician for the St. Louis F.C. professional soccer team for the last five years. He has also provided game coverage for numerous NCAA and other local sporting events.


Dr. Greiner lives in the city of St. Louis with his wife Meaghan.

Dr. Horn’s involvement with sports goes back to his undergraduate days at Notre Dame, when he worked as a student manager for the football and tennis programs.


Now in his second season with the Cardinals, he’s passionate about helping patients, especially young adults and athletes, achieve peak performance on and off the field. He enjoys working in collaboration with psychologists and mental strength coaches to promote wellness and preventive care. In his 12 years of practice, he’s worked at all levels of mental health care, developing collaborative care models for the primary care setting. He currently serves as medical specialties chair and director for outpatient psychiatry services regionally with Mercy. 


Dr. Horn is the Medical Specialties Chair  and Director of Outpatient Psychiatry Services at Mercy Clinic Psychiatry in St. Louis and Jefferson, MO. He has a BA from the University of Notre Dame, a DO from the University of North Texas Health Science Center an did his psychiatry residency at the University of Oklahoma -- Tulsa.


Dr. Horn lives in St. Louis with his wife Maggie and their children Liam, Grace, Brigid, Andrew and James. He’s an avid tennis player and volunteers his time with scouting programs. 

Dr. Brian Mahaffey has been a member of the St. Louis Cardinals medical staff as a Team Physician for eight years. He serves the Cardinals organization as Coordinator of Major League Medical Services. Prior to coming to St. Louis, he served as Team Physician with the Springfield Cardinals (double AA affiliate) in Springfield for 11 years.


Dr. Mahaffey is Medical Director of Mercy Sports Medicine and is with Mercy Clinic Sports Medicine.


Dr. Mahaffey’s interest in baseball is life-long. He attended Missouri State University (MSU) where he played baseball while earning a BS in biology. He was named Conference Co-Player of the Year in 1988. In 2005, he was inducted into the MSU Athletic Hall of Fame, and in 2014, into the initial class of MSU’s Academic Hall of Fame for Athletics. In 2019, Dr. Mahaffey was inducted into the Missouri Sports Hall of Fame.


Dr. Mahaffey graduated from the University of Missouri – Columbia School of Medicine, holds a Master of Science in Public Health from MU, completed a residency in family and community medicine at MU, a fellowship in Sports Medicine and Academic Medicine at MU, and earned a Primary Care Sports Medicine Certificate of Qualifications.


Before moving to St. Louis, Dr. Mahaffey helped develop a regionally known sports medicine program with Mercy in Springfield. He also served as Head Physician for the MSU athletics program for 16 years.


Originally from Springfield, Dr. Mahaffey and his wife, Sandra, live in the St. Louis area. They have two daughters: Lauren and Samantha.

A two-time Academic All-American lacrosse player and an NCAA Scholar as an undergraduate, Dr. George Paletta is a nationally and internationally recognized orthopedic surgeon specializing in Sports Medicine.


Dr. Paletta has extensive experience in both academic and private practice. In 1996, he began his practice at Hospital for Special Surgery. From 1998-2005, he served on the faculty of Washington University School of Medicine (Department of Orthopedic Surgery) as Chief of Sports Medicine and Director of the Sports Medicine Fellowship.  In 2005, he joined The Orthopedic Center of St. Louis, a private practice group.


He’s served as team physician for the New York Mets (1996-1998), the St. Louis Rams (1998-2003) and Head Team Physician for the St. Louis Cardinals (1998-2014). In 2016, he became the Cardinals’ Head Team Orthopedic Surgeon. 


Mercy Clinic Orthopedics – Sports Medicine


  • BA, College of the Holy Cross, 1984
  • MD, Johns Hopkins University School of Medicine, 1988
  • MBA, Washington University 2015
  • General Surgery Internship, Northwestern University Hospital, 1988-89
  • Orthopedic Residency, Hospital for Special Surgery, 1990-94
  • Fellowships:
    • Hospital for Special Surgery (sports medicine research), 1989-90
    • Cleveland Clinic (adult sports medicine), 1994-95
    • Children’s Hospital of Michigan (pediatric sports medicine), 1995-96

Dr. Shalen Kouk joined the St. Louis Cardinals medical staff in 2023 and serves as a team orthopedic surgeon.


Dr. Kouk earned his undergraduate degree from Cornell University in Ithaca, New York, and his medical degree at Case Western Reserve University Medical School in Cleveland, Ohio. He then completed his Orthopedic Surgery residency training at NYU Langone Medical Center in New York City and his Sports Medicine fellowship in Birmingham, Alabama at the American Sports Medicine Institute and renowned Andrews Sports Medicine Center. 


Prior to joining the Mercy Clinic, Dr. Kouk cared for athletes from high school, NCAA Division I collegiate and professional sports. He has written several publications and book chapters focusing on treatments for orthopedic injuries as well as UCL (ulnar collateral ligament) repair, also known as Tommy John surgery, in baseball players.


Dr. Kouk lives in St. Louis with his wife, who is a urologic oncologist.

Dr. Steffes is in his first year with the St. Louis Cardinals medical staff as a Team Orthopaedist. Prior to joining the team, he served as an assistant team physician for both the Los Angeles Dodgers and Angels baseball clubs.


Dr. Steffes is with Mercy Clinic Orthopaedic Surgery. He received his medical degree from Wayne State University and completed an orthopedic residency at the University of Illinois. Dr. Steffes then completed an orthopedic sports medicine fellowship at the Kerlan-Jobe Orthopaedic Clinic where he provided care for the Los Angeles Rams, Galaxy, Sparks, Dodgers, Angels, Anaheim Ducks, PGA Tour. At the collegiate level, he has been a part of the medical team for the University of Southern California, Loyola Marymount and Pepperdine Universities.


Dr. Steffes lives in St. Louis with his wife, Marcella, and their family.

Dr. Christian Verry is in his inaugural year with the St. Louis Cardinals medical staff, serving as a Team Physician.


Dr. Verry is core faculty with Mercy family medicine residency, and an adjunct assistant professor at Saint Louis University School of Medicine, Department of Family and Community Medicine. He also serves as medical director for Hotel California by the Sea, a local addiction treatment center.


Dr. Verry earned his medical degree from the University of Missouri-Columbia and completed a family medicine residency at Swedish Family Medicine in Littleton, CO. He also completed a sports medicine fellowship at the University of Oklahoma at Tulsa.  He holds a certificate of added qualifications in sports medicine.


During his career, Dr. Verry has cared for athletes in a variety of settings. He has served as head team physician for the University of Vermont, as team physician for Saint Louis University and as part of the medical team for the St Louis Ambush. He has also provided coverage for numerous semi-professional and NCAA events.


Dr. Verry lives in the St Louis area with his wife, Teresa, and their three young boys.