The linebacker was cut from the team following three seasons with the Raiders, having been selected in the first round of the 2010 draft.
The 23-year-old said in a statement: "I'd like to thank the Raiders for giving me an opportunity to play in the NFL.
"I'm disappointed that it hasn't worked out better, but I'm very excited and thankful for the Raiders allowing me to get a fresh start.
"I will miss my teammates and wish them and the Raiders organisation good luck going forward."
McClain made 62 tackles during the 2012 season, including one sack and a forced fumble.