"It's terrible," Rivera said Friday. "It's absolutely terrible. Our thoughts and prayers go out to him and his family, and hopefully things work out. Hopefully, it's not a distraction -- because it's a very young life and it's a very personal family situation."
"He's to me a mixture of those types of guys, but I'm still partial that the greatest of all time is Walter Payton," said Rivera, a linebacker for the Chicago Bears from 1984-92.
On Sunday, Rivera will be concerned with how to stop Peterson. On Friday, he was concerned about Peterson's personal well being.
"I will say this," Rivera said. "In my opinion, he couldn't be with a better coach as far as a very spiritual man. Leslie [Frazier] will help him through this situation and this circumstance because of the person Leslie is."
Rivera and Frazier were teammates on the 1985 Bears Super Bowl team. They have remained close friends through the years.
But on Sunday, it will be business. Rivera will try to beat his good friend and stop a running back going through a tough personal experience.
"You have to," Rivera said. "I don’t want to sound callous or anything like that, but you have to. It’s the unfortunate nature of the game."