Bill Peduto -- the mayor of Pittsburgh and a longtime Le'Veon supporter -- tells TMZ Sports he's beginning to think the Steelers don't need the RB to make a Super Bowl run.

"James Conner's proving to be a worthy back and it's a team sport," Bill says. "It's beyond one player."

It's a bit of a surprising claim ... considering Bell has nearly 8,000 yards from scrimmage in 62 career games ... but Bill -- like some of Bell's own teammates -- seems to be fed up with the holdout.

"He's, I think, getting very bad advice from his manager," Peduto tells us.

"It's getting to the point of a certain tipping point when you can still come back and your teammates and the fans will want to have you back."

As for Bell ... probably doesn't care what Peduto has to say -- he still wants to get paid. Plus, it's hard to hear the critics above the roars of a jet ski!!!!!!