ENGLEWOOD, Colo. -- A lot of people ask Denver Broncos quarterback Peyton Manning how he'll decide when to end what will be a Hall of Fame career.

After all, he's 38 years old, has had four neck surgeries and is on the doorstep of his 17th NFL season. But Wednesday, Manning said he might adopt Patriots quarterback Tom Brady's recent thoughts on the matter. Perhaps it could be known as the Brady principle.

"[Tom] Brady said he was going to play until he ... sucked. That's a pretty good line. I'm kind of the same feel. I don't have a set number. ... Yeah, right until you suck -- I think that's a pretty good rule right there."

On his weekly radio appearance on Boston's WEEI earlier this week, Brady addressed his career plan: "I love playing for this team and I love representing this team, and hopefully I can do that for as long as I can. When I suck, I'll retire. But I don't plan on sucking for a long time. So hopefully that leads me to being here, and there's no place I'd rather be."

After Wednesday's practice, Manning was asked about the league's current elder statesmen at quarterback -- such as himself, Brady and New Orleans Saints quarterback Drew Brees -- possibly playing into their 40s.

"Brady said he was going to play until he ... sucked," Manning said with a smile. "That's a pretty good line. I'm kind of the same feel. I don't have a set number.

"Some guys can hang on, can hang on and hang on and get another year vested, I guess, if that's the goal. If you can really produce and help a team, and you enjoy playing, I think that's up to the individual."

Minutes later he said, "Yeah, right until you suck -- I think that's a pretty good rule right there."

Manning wasn't sure whether rules changes designed to protect the quarterback would help his longevity cause.

"There's no rule how hard these guys can hit and how fast these guys can run," Manning said. "If you can't make a throw in front of a cover corner and you can't get up from a blindside hit, you're not playing very long, anyway."