Hall of Famer
Last year Kelly had some teeth and part of his jaw removed due to oral cancer.
Kelly's wife, Jill, wrote on her personal blog last week that "the cancer's back, aggressive, and starting to spread."
Family friend Dennis DiPaolo told WIVB-4 in Buffalo that Kelly is weak and in a lot of pain but is keeping his spirits up.
"He's like, 'Come on, don't hang your heads,' " DiPaolo said. "Like you walk in the room and he's in a huddle and still commanding everyone and even if he's trying to rest his eyes, he knows you're there and he goes, 'Thanks for coming you guys.' He's just a remarkable individual."
Kelly was visited at home last week by some of his former Buffalo Bills teammates, including Thurman Thomas,
Another Hall of Fame quarterback from Kelly's era,
Kelly is a five-time Pro Bowler who took the Bills to four straight Super Bowl appearances from 1990 to 1993. He became a first-ballot Hall of Famer in 2002.