Former New York Giants cornerback Terrell Thomas, who overcame three separate ACL tears to return to continue playing in the NFL, formally announced his retirement at age 30 on Thursday.

After recovering from a torn right ACL suffered in college at USC, Thomas was a promising defensive back who had five interceptions for the Giants in both 2009 and 2010. But he tore that same ACL in the preseason in 2011, and after rehabbing and returning the following year, he tore it again in training camp in 2012.

Terrell Thomas is believed to be one of only two players to recover from three ACL repairs in the same knee to return to play in the NFL. Brad Mills/USA Today Sports

Those injuries cost him two full seasons, but he returned in 2013 to play in all 16 games for the Giants as their nickel cornerback. He was named NFC defensive player of the week for his performance in the Giants' Week 8 victory in Philadelphia that year.

But after 2013, Thomas couldn't find work. He drew interest from a few teams, including the Carolina Panthers and Seattle Seahawks, but he did not play in 2014. In a news release issued Thursday by the Giants, Thomas said his knee was the reason.

"I thought I was going to have an active free agency," Thomas said. "The number one thing was the doctors would not approve my knee. Every team, GM, coaches, they loved me and wanted me, and thought I had a great year after coming back from all the ACL injuries. They thought that I would be better last year. But the doctors wouldn't approve me.

"Knowing the game of football, being 29 with three ACL [injuries], I just figured my time is short. I can keep chasing a dream, but I was blessed to be able to come back and play that one year. To be able to show my family and fans, my daughter and myself that I worked hard enough to overcome some significant injuries and I became the second player in NFL history to come back from three ACLs. I didn't play with a brace. I am proud of my accomplishments. I have been through a lot, and I overcame it.

"I am a smart dude, and I am not going to chase football. Football is not chasing me. I feel like my time is over. I was blessed enough to play six years in the NFL. I lived my dream, and now it is time for the next chapter of my life."

Thomas and Panthers linebacker Thomas Davis are believed to be the only players ever to recover from three ACL repairs in the same knee to return to play in the NFL.