Aug. 7, 2014: In this file photo, Montreal Alouettes' Michael Sam and teammates warm up for a Canadian Football League game against the Ottawa Redblacks in Ottawa, Ontario. (Justin Tang/The Canadian Press via AP)

MONTREAL –  Michael Sam is stepping away from pro football.

Sam, the first openly gay player drafted by the NFL, has told the CFL's Montreal Alouettes that he is leaving the team. He tweeted Friday that "The last 12 months have been very difficult for me, to the point where I became concerned with my mental health. Because of this I am going to step away from the game at this time."

He did not play in Montreal's game against Edmonton on Thursday night, citing a sore back. He made his CFL debut the previous week.

Sam was selected in the seventh round of the 2014 NFL draft by the Rams, did not make the team, and spent some time on the Cowboys' practice squad before being released.