Michael Sam, the first openly gay player to be drafted by an NFL team, announced on Friday evening that he is stepping away from football, citing mental health reasons.

"The last 12 months have been very difficult for me, to the point where I became concerned with my mental health," Sam wrote in the first of a series of tweets.

"Because of this, I am going to step away from the game at this time. I thank the Alouettes for this opportunity and hope to be back on the field soon. Thank you all for your understanding and support."

As noted by a CBSSports.com report, Sam was a consensus All-American and SEC Defensive Player of the Year during his final season at Missouri. He was eventually drafted in the seventh round of the 2014 draft by the St. Louis Rams.

Sam held his own in the Rams' preseason games, finishing the run with 11 tackles and three sacks, but was ultimately beat to a roster spot by undrafted rookie Ethan Westbrooks.

Sam moved on to be a practice player for the Dallas Cowboys, where he stayed on as a member of the practice squad from Sept. 3 to Oct. 21, then was released when Cowboys defensive end Demarcus Lawrence came back from the injured list.

The carries on noting that after being unsigned for the rest of the 2014 season, Sam applied to participate in the NFL's maiden veteran combine, which was held at the Arizona Cardinals' team facility last March.

Sam was still left out of an NFL roster following the combine, where he ran the 40-yeard dash in 4.99 seconds He then signed with the Montreal Alouettes of the Canadian Football League, becoming the league's first openly gay player to play in a regular season game. He did not register any tackles or sacks in the games he played for Montreal.