Montreal Alouettes defensive end Michael Sam is stepping away from football, one week after becoming the first openly gay athlete to play in a professional football game.

Sam took to Twitter on Friday to announce his decision, citing his mental health as a concern. '

He missed the Alouettes' game on Thursday due to a back injury.

Sam, a seventh round pick of the St. Louis Rams in the 2014 NFL Draft, made his professional debut against the Ottawa Redblacks on Aug. 7. He failed to record a tackle or sack while taking a handful of snaps.

The 25-year-old was cut by the Rams after the preseason in 2014 but was signed to the Dallas Cowboys practice squad, where he spent one month before being cut. After attending the NFL's veteran combine in March 2015 and failing to garner interest, Sam headed north of the border and signed with the Alouettes in May.

His decision to walk away ends a tumultuous season with the Alouettes. He appeared in just game and was suspended in June for leaving Alouettes training camp for personal reasons. He returned to the team 13 days later and finally saw first game action last week.

The Als placed Sam on the team's suspended list after his Friday announcement, retaining his rights should he return to the CFL.