He was suspended indefinitely in December 2016 for violating the league's substance-abuse policy.
That came after he missed four games in 2015 and received a 10-game ban to start the 2016 campaign for also violating the substance-abuse policy.
Having last played in 2015, the former first-round pick let it be known earlier this year that he was looking to revive his career.
"I'm nowhere near satisfied with how my professional career has gone," McClain told Matt Zenitz of AL.com in July. "That's for myself. That’s me looking in the mirror and talking to my boys. Nah, that's not the taste I want to leave in my mouth."
Taken eighth overall in 2010, McClain spent the first three seasons of his career in Oakland. He averaged 82 tackles per season for the Raiders, highlighted by a 100-tackle, five-sack performance in 2011.
He signed with the Baltimore Ravens shortly after being waived by the Raiders. However, he never played a down for the Ravens as he retired a month later.
McClain returned to football after being traded to Dallas in July 2014. He appeared in 24 games over the course of the 2014 and 2015 seasons, piling up 167 tackles, three sacks and three interceptions for the Cowboys.
Unfortunately for him, his resurgence was cut short by multiple substance-abuse suspensions.
Dallas still owns McClain's rights, though ProFootballTalk's Charean Williams reported the Cowboys are expected to release the 30-year-old once they are officially notified by the league of his reinstatement.