PITTSBURGH — The play might not have happened in September. Stephon Tuitt might not have been ready. Vince Williams might not have even been on the field.

Yet there Tuitt was last Sunday, the Pittsburgh Steelers rookie defensive tackle slamming into Kansas City running back Jamaal Charles in the third quarter of a four-point game. There was Williams, a second-year linebacker who wasn’t part of the plan a few weeks ago, pouncing on the ball. There were the Steelers reclaiming momentum and a 20-12 victory that assured them of a return to the playoffs after a two-year absence.

“That was an awesome moment, a spectacular moment of the game,” Tuitt said. “I’m glad I could be a part of it.”

Something that’s happening with increased regularity over the last two months as Pittsburgh (10-5) surged toward the postseason. The influx of youth the Steelers needed to overhaul an aging roster is starting to mature. Each weekend, a bevy of 20-somethings have propelled the franchise back to relevance after consecutive 8-8 seasons.

Pittsburgh can win the AFC North with a victory over Cincinnati (10-4-1) on Sunday night. It would be the franchise’s first division title since 2010. That’s not considered a drought in most places. Then again, Tuitt knows he doesn’t work in most places. The main hallway at the team headquarters is the only spot in the world where there’s a display filled with a half-dozen Vince Lombardi trophies.

Those seven-pound, 22-inch symbols of greatness are a constant reminder the team didn’t alter its definition of success even as it underwent a seismic roster shift following a wild card loss to Denver in the 2011 playoffs.

Only 21 players remain from the group that walked off the field in stunning disbelief after Tim Tebow — yes, Tim Tebow — and Demaryius Thomas hooked up for an 80-yard catch and run that brought a solid season to a crushing end. In the place of Hines Ward, James Farrior and Aaron Smith is a collection of young 20-somethings like Tuitt and Williams, forced to learn on the fly.

The growing process hasn’t always been pretty. There was the collapse down the stretch in 2012 that included five losses in the last seven games. The 0-4 start that ended 2013 before it really began. The baffling upset at the hands of Tampa Bay in Week 4.

Getting through it wasn’t easy. Yet linebacker Sean Spence — who missed all of 2012 and 2013 with a knee injury — believes it might have been unavoidable. The only way to learn is to be on the field. There’s no film preparation that can replace having to get out there and actually do it.

The film sessions and practices that accompanied Pittsburgh’s erratic 3-3 start were difficult. Without them, however, Spence isn’t sure the Steelers are back in the playoffs.

“A lot of young guys have been playing. That can be good and bad. But I think that’s been good for us,” Spence said. “We went through those growing pains early in the season, losing close games, letting teams come back instead of keeping them down when they was down. I think that’s paid off a lot.”

Pittsburgh has outscored the opposition 35-13 in the fourth quarter of its three-game winning streak. All four of the touchdowns have come courtesy of 22-year-old running back Le’Veon Bell and the 23-year-old wide receiver Martavis Bryant. Both were still college underclassmen the last time the Steelers won a playoff game. Both will be relied on heavily as the Steelers prep for January.

“This is about development and about evolving as the season goes on,” offensive coordinator Todd Haley said. “It’s an evolution and it’s guys growing into their roles, understanding their roles sometimes.”

Even if they can vary from week to week. The Steelers were so frustrated by the slow development along the defensive line they brought back Brett Keisel near the end of training camp and re-signed 36-year-old James Harrison following injuries to Ryan Shazier and Jarvis Jones.

Keisel’s season is over with a torn triceps and Jones and Shazier are now healthy. Yet Williams has played his way into the rotation and Tuitt’s growth over second half of the year has him playing meaningful snaps in meaningful games. The kids are growing up just in time.

“You have to give them credit,” defensive coordinator Dick LeBeau said. “They stuck through the ups and downs.”