Buffalo Bills linebacker A.J. Tarpley will retire from the NFL after one season, citing a concern for his health due to concussions.
Tarpley, 23, made the announcement via his Instagram account on Wednesday.
"The only thing comforting about not knowing this play would be the last of my career, is knowing that I never took a second for granted," he wrote in the post, which included a photo of him playing Week 17 against the Jets.
"After months of introspection, I am retiring from football. I suffered the 3rd and 4th concussions of my career this past season and I am walking away from the game I love to preserve my future health.
"This decision is the hardest I've made yet but after much research and contemplation I believe it's what is best for me going forward."
Signed last off-season by the Bills as an undrafted free agent out of Stanford, Tarpley appeared in 14 games in 2015, starting two.
He tallied eight tackles, a sack, a forced fumble and a pair of interceptions.
Tarpley played four seasons at Stanford, where he said he had suffered his first two concussions.
"I'd like to extend my gratitude to everyone that helped me along the way. Thank you to my coaches at Wayzata and Stanford, and to lifelong friends that I was blessed to call teammates. You all molded me into the man I am today," he added.
"To my family, I'll never be able to repay your unwavering support and love, I just hope that I can continue to show how gracious I am and make you proud.
"I also want to thank the Buffalo Bills organization, coaches, and teammates for helping me fulfil my lifelong dream in the NFL. Last but not least, I'm proud to be a part of #BillsMafia and playing in front of the best fans in the league is something I won't forget. Thank you God for all that you have blessed me. I'm excited for my future."
Tarpley's early retirement continues a trend of young NFL players retiring early because of long-term health concerns from concussions they had suffered during their time in the league.