The first openly gay player drafted by a National Football League side says he is stepping away from the sport because he is concerned over his mental health.
Michael Sam, 25, signed a two-year deal with Canadian Football League's Montreal Alouettes in May, but the club said on its team website he had left for personal reasons.
The defensive lineman was suspended in June after he left their training camp.
"The last 12 months have been very difficult for me," he said on Twitter.
"I became concerned with my mental health.
"Because of this I am going to step away from the game at this time. Thank you all for your understanding and support."
Sam was the Southeastern Conference Defensive Player of the Year as a senior at the University of Missouri before graduating in December 2013.
The following February before the NFL Draft, he announced he was gay.
St Louis Rams selected Sam in the seventh round of the 2014 draft but waived him in the final round of cuts.
He was picked up by the Dallas Cowboys but they released him from their practice squad in October.