JC Tretter, president of the National Football League Players Association (NFLPA), has called time on his playing career.
Tretter, who was a fourth-round pick for the Green Bay Packers in the 2013 draft, was released by the Cleveland Browns in March after spending five seasons with the team.
The 31-year-old was elected president of the NFL's labour union in March 2020, winning a second term earlier this year after playing a key role in negotiating the league's latest collective bargaining agreement and in creating health and safety protocols during the COVID-19 pandemic.
The center, who played 81 games for the Browns, told his social media followers he would now be looking to focus on his off-pitch responsibilities.
"In May 2011, I wrote myself a letter. Today, May 7, 2011, 2:35am you decided that you will become a professional athlete. You will get drafted and you will play in the NFL until you want to stop," he posted in a message on Twitter.
"I have decided to fulfil the second part of my letter, to stop playing when I wanted to – on my own terms.
"I feel like if my 31-year-old self could talk to my 20-year-old self, I could earnestly tell him that we did it. We did everything we said we'd do and more.
"My time on the field may be over, but I'm not stepping away from football.
"I'm looking forward to doubling down on my work as NFLPA president and pushing for more progress on behalf of the great players of our game, past, present, and future."