As an outside linebacker for the Chicago Bears, Rivera had only five tackles and no sacks in two games against Kelly during the late 1980s and early 1990s.
But like many who are pulling for the Hall of Fame quarterback as he battles oral cancer, Rivera remembers how tough Kelly was.
"A very tough guy,'' Rivera said last week at the NFL owners meeting in Orlando, Fla. "To see a guy get hit, get knocked down and get back up is always impressive. In my era -- shoot, it sounds like I'm old now -- but in my era you looked at certain guys that had that swagger about them.
"John Elway used to get knocked down, get up, straighten up his head and he'd walk back to the huddle. Jim Kelly, I can remember the same thing watching him in those [four] Super Bowls. ... You never let 'em see you're hurt.''
Rivera knows Kelly, 54, is hurting now. He hopes the toughness Kelly showed as a player gets him through the cancer.
Hearing of Kelly's illness also is a reminder that there are many from his playing days (1984-1992) that are going through medical issues, including former Bears quarterback Jim McMahon.
McMahon admitted last year he was going through early stages of dementia believed to be the result of head trauma suffered during his career.
"We're now at an age, I'm now at that age, guys that I played with are getting ill,'' said Rivera, 52. "Guys that I played with are getting hip replacements, knee replacements, shoulder replacements ... I don't want to say it's scary, but it is.
"So when you see a guy like Jim Kelly [and] Jim McMahon struggle with health issues, it's a scary thing.''