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Mike Adams was standing on the sideline, minding his own business when his NFL career got a kick-start.

A minute after Pittsburgh Steelers starting right tackle Marcus Gilbert went down with a hyperextended right knee early in the season opener against the Broncos, Adams found himself lining up across the line from Denver's all-everything linebacker, Von Miller.

Gulp.

"I didn't expect it, but you've got to be ready to play whenever," Adams said. "It was a pretty cool experience."

One that included some very public growing pains as Adams and the rest of the offensive line were roughed up late in a 31-19 loss. The film session was long and painful, with offensive line coach Sean Kugler giving the second-round draft pick out of Ohio State some very pointed criticism.

The talk was a watershed moment for a player not known as a workaholic during his time with the Buckeyes. Adams responded with a tenacity that proved to the guys lining up next to him he was serious about this whole NFL deal.

Good thing considering Adams will make his first start Sunday when Pittsburgh (2-3) travels to Cincinnati (3-3). Gilbert is out indefinitely with an ankle injury.

"Mike's day-to-day stuff has changed a whole lot," Pittsburgh guard Ramon Foster said. "He's more in tune to what's going on. Not to sound bad, but him getting embarrassed like (in Denver) kind of woke him up a little bit. He got chewed out pretty good and he's come back pretty strong from it."

The massive 6-foot-7, 323-pound Adams has long had the athletic ability to flourish. The only concerns were about his attitude. He acknowledged flunking a drug test just before the NFL combine last spring and was suspended a handful of games during his final season at Ohio State for his role in the scandal that eventually led to coach Jim Tressel's dismissal.

Adams pledged during minicamp that he'd put his troubled past firmly behind him and he's backed it up by becoming an eager student of the game. Following practice on Wednesday Adams joined starting left tackle Max Starks and rookie Kelvin Beachum for extra reps taking whacks at a heavy bag at one end of the practice field.

It's a ritual that Adams has joined in repeatedly since training camp, and with his huge wingspan he swatted the bag around like a toddler playing with a favorite toy. On Sunday, that bag will morph into Cincinnati defensive end Carlos Dunlap, who is part of a unit that is second in the NFL with 21 sacks.

No pressure or anything, though Adams pointed to Dunlap's 6-6 frame as something he can get a handle on better than the smaller, speedier Miller. Besides, just about anything Adams faces in a game will be easier than the time he's spent over the last month trying to block James Harrison or LaMarr Woodley in practice.

"When you're going against two of the best in the world, it's easy to learn fast," Adams said. "They're great vets. They teach me things on the go."

The Steelers pride themselves on the way they bring each other along, and Adams doesn't need to look too far for someone who knows exactly what he's going through. A year ago, Gilbert was a rookie tackle thrust into the starting lineup by injury. By the end of the season, he was starting on merit.

Adams said he and Gilbert are "close" and it's clear the team intends to have the two serve as bookend tackles at some point down the road.

At the moment, the Steelers need Adams to do his best Gilbert impression and just hang in there for a team that is banged up all over the place. Adams might not even be the only backup lineman playing for a team facing a critical juncture early in the season.

Doug Legursky practiced at center on Wednesday in place of Maurkice Pouncey, who is questionable with a right knee injury. Putting together a patchwork offensive line is nothing new in Pittsburgh, where the practice seems to be as much a part of the football season as the Terrible Towel.

"It always seems to happen to us, it does," Foster said. "We've got to reverse this curse, whatever is going on. We've handled it before."

The Steelers have to handle it again if they want to keep pace in a ridiculously crowded AFC, where nine teams have three losses six weeks into the seasons. The Bengals are one of them, though a win over Pittsburgh would give Cincinnati some breathing room in a suddenly vulnerable AFC North now that division leader Baltimore has lost linebacker Ray Lewis and cornerback Ladarius Webb for the season with injuries.

Adams' job will be to help keep pressure off quarterback Ben Roethlisberger and open up holes for a running game that has operated in fits and starts. It's a job he's ready for, even if his opportunity to step under the lights came a little earlier than he expected.

"I think for Mike, this is the perfect process and perfect time for him to come in and start playing," Starks said.

NOTES: Safety Troy Polamalu will miss his fourth game of the season with a strained right calf, though Polamalu said Wednesday he remains optimistic he won't be sidelined for a significant amount of time ... Running backs Rashard Mendenhall (right Achilles) and Isaac Redman (ankle) did not practice on Wednesday though both are questionable ... Linebacker Lawrence Timmons did not practice on Wednesday with a foot issue.

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Follow Will Graves at www.twitter.com/WillGravesAP