He shared the news on Instagram:
Tarpley said in his post he suffered the third and fourth concussions of his career last year and explained he was "walking away" from the gridiron "to preserve [his] future health."
Tarpley expanded on his decision to retire on Tuesday via MMQB:
This was not about me thinking I couldn’t physically play more football without suffering crippling brain damage. I have no current residual effects that I am aware of, cognitively or physically. The decision I made to retire from football is about coming to terms with the totality of my concussion history and what is asked of me as a linebacker. My position put me at an elevated risk for further injury with the likelihood that I would be exposed to hundreds or even thousands of similar situations. I understand that in order to continue playing at the level expected of me, I would have had to put myself in those exact scenarios.
I will never know if I would have received life-impairing damage to my brain somewhere down the line. There is a chance I could have played five more years in the NFL and lived a long, happy and healthy life. But going forward my life will be entirely what I make of it. My happiness is in my hands.
The Bills confirmed his retirement on April 7.
The 23-year-old went undrafted out of Stanford in 2015 but made a considerable impact under the circumstances. Tarpley appeared in 14 games for the Bills, recording eight combined tackles, two interceptions, one sack and a forced fumble.
As he mentioned in the Instagram post, Tarpley made the final defensive play of the Bills' season when he intercepted New York Jets quarterback Ryan Fitzpatrick in Week 17. Buffalo won the game 22-17 and denied its AFC East rival a chance at securing a playoff berth.
Tarpley isn't the first player in recent memory to retire early because of concerns about traumatic head injuries. Former San Francisco 49ers linebacker Chris Borland walked away last offseason after only one year—and he was San Francisco's leading tackler as a rookie.
There are bound to be additional players who go the way of Borland and Tarpley. Linebackers in particular are at the epicenter of the action, with the NFL's leading tacklers making over 100 tackles per season.
A top NFL official acknowledged the link between head injuries and playing football for the first time in March. As more research surfaces in the coming years, the true extent of the damage football can do should be revealed, which may make Tarpley among the first of many who retire in short order.
But considering Tarpley had a known history of multiple concussions and could have left himself susceptible to further damage the more he played, his individual case seemed suited for retirement—as opposed to a player who doesn't have a documented concussion history.