Veteran Indianapolis Colts quarterback Kerry Collins said Monday he's "99 percent sure" that he will retire for a second time.
"When you start dealing with concussions at my age and this point in my career, I'm inclined to think this is going to be it for me," Collins said, according to the Indianapolis Star.
"I just didn't respond the way everybody had hoped," Collins said. "It just took longer. Some symptoms just lingered. There was concern that since it did take so long, in the future there would be a real possibility of longer-term damage.
"(Concussions) hadn't been a big part of my career, but this one was significant."
Collins will be paid $4 million for his brief stint with the Colts, who scrambled to sign him out of retirement when the season started after learning that Peyton Manning would not be ready to play anytime soon.
"I have no regrets and I have a clear conscience," Collins said. "It's been really good to play for this organization. ... I just wish I could have helped out a little bit more."
Collins completed 49 percent of his passes for the Colts, throwing for two touchdowns, one interception and a 65.9 passer rating.