The veteran defensive end is finishing his 12th NFL season, and he and inside linebacker Larry Foote are the only players left from the Steelers' 2002 draft class.
Keisel has become one of the faces of the Steelers -- his beard has taken on a persona of its own -- and he is such a fixture on the team that it's easy to forget how tenuous his standing once was in Pittsburgh.
Keisel nearly left his first training camp because he was so overwhelmed as a seventh-round draft pick who had to make the transition from a 4-3 to 3-4 defense. Even after Keisel had established himself as a core special-teams player, he went to one extreme to make sure his work on that unit didn't slip at all.
The Steelers wanted Keisel at a certain weight so he could handle the snaps he was also getting as a defensive end in their sub-packages. Keisel feared that the extra bulk could compromise his play on special teams, so he would slip a 10-pound weight into his shorts before weigh-ins.
"That year we won the Super Bowl [2005 season], I was mostly a situational substitute. I would come in on third downs and rush the passer, because I was lighter then," said Keisel, who is in the last year of his contract. "My job to that point was running down on kickoffs and I needed to be fast."
Indeed, Keisel wasn't trying to pull one over on the coaching staff as much as he was doing what he felt he needed to do to survive in the NFL.
It is worth revisiting the path Keisel took to get where he is for this reason: Fans who attend the game Sunday need to give him his due in case it is his last game in a Steelers uniform.
Consider what Dick LeBeau recalled after returning to the Steelers in 2004 for a second stint as their defensive coordinator.
"There were two guys in here every day, Brett Keisel and James Harrison," LeBeau said. "They both ended up being pretty dang good football players, and neither one of them had anybody heard too much about."
That is not to say that Keisel is merely a product of hard work. The 6-foot-5, 285-pounder's athleticism is such that the Steelers experimented with him at outside linebacker after 2006, his first season as a starter.
"He could have been a very good outside linebacker in our system, without a doubt," LeBeau said. "He's got the space coordination [ability to play in space] and great hands. If you don't get him cut off, he's going to get to the ball no matter where it is on the field. He's got great range."
His career is proof of that.