The Steelers are currently sitting pretty at the top of the AFC North with Aaron Rodgers under center -- a feat some didn't believe the 41-year-old quarterback could pull off ... but Jerome Bettis tells TMZ Sports he never doubted the player, only the body.

We caught up with the Pittsburgh legend this week at LAX ... and chopped it up about his former team lookin' pretty damn good so far this season, thanks to Rodgers' 17 touchdown passes. Getty

Given Rodgers' underwhelming stint with the Jets last season, his resurgence has shocked plenty of fans ... but according to Bettis, you never count out a QB like him.

"When you've been a great player in the league, you don't forget how to play," Bettis said. "I don't think that was ever a question. I think the question was 'Can h

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