James Harrison congratulated by coach Mike Tomlin

Pittsburgh Steelers linebacker James Harrison (92) is congratulated by Steelers head coach Mike Tomlin following Harrison's 100-yard interception return for a touchdown during the second quarter of the NFL Super Bowl XLIII football game, Sunday, Feb. 1, 2009, in Tampa, Fla. (AP Photo/Amy Sancetta)

PITTSBURGH -- Much of James Harrison's career has been an exercise in shattering supposed limitations.

The latest comes in the form of the snap count cap Pittsburgh Steelers outside linebackers coach Joey Porter placed on his former teammate. During the NFL Draft, Porter said he will try to limit Harrison to 25 snaps per game.

He thinks he can do more, though, and for a really long time.

"I think I can play more than 25 snaps a game when I'm 50," Harrison said.

After Tuesday's organized team activities, Harrison, 37, discussed his role as a mentor to the team's younger linebackers and his place in the team overall. Harrison said he's not a particularly verbal leader and that he prefers to show players how to do their job with what he does in practice.

Harrison - who retired after the 2013 season only to return to the Steelers mid-injury crisis - also reiterated that he doesn't want to be a backup, no one does.

"I show what I do by going out there and actually doing it," Harrison said. "I don't talk to you about it, I do it. So if you just watch what I do, it really shouldn't be that hard to do the things that's necessary."

His workouts have impressed the team's first-round draft pick, Bud Dupree, who stays away from Harrison in the weight room

The younger linebackers on the team have been asking him question about the defense, they've been receptive and it's what he expected.

Harrison wasn't at practice last Wednesday

Or Thursday

Harrison said he isn't making getting a certain number of snaps as a challenge, but anyone who's content to be a backup player is in the wrong profession.

It makes the 2015 season, Harrison's 13th, just another in his career of breaking doubts.

"That's the road I've took so to speak," Harrison said. "It's nothing different. You can say I can't do this, I can't do that, I'm too old to do this, too old to do that, but I'm still here."