Denver Broncos wide receiver Demaryius Thomas celebrates after scoring on a two-point conversion late in the game. (Matthew Emmons/USA Today Sports)

Because there are still hints of poetry to be found in a bruising, unforgiving game, the final chapter of Peyton Manning’s stellar career will either start or finish with the only adversary who makes sense: his antagonist, his thorn, his equal. To reach the Super Bowl, to reach retirement or to reach an offseason of uncertainty, Manning must first face Tom Brady.

With the Denver Broncos’ 23-16 win over the Pittsburgh Steelers on Sunday, next weekend’s AFC championship game likely will be the final installment in one of the game’s greatest quarterback rivalries. Manning-Brady: the best of their generation, everything on the line . . . a heavyweight showdown packed with glitz, glamour and gridiron prestige.

Or maybe not. Manning-Brady XVII will punch one man’s ticket to Super Bowl 50, but despite the high stakes, Manning showed again Sunday why next weekend’s quarterback quarrel won’t likely match the classic showdowns that have preceded it.

Brady is as essential as ever to New England Coach Bill Belichick’s master plan. He’s not a chess piece as much as he’s Belichick’s chessboard. In Denver, however, the 39-year-old Manning is suddenly a cog — a cross-your-fingers, squint-your-eyes prayer each time the ball is snapped. But for now, that was enough to dispose of a banged-up Steelers squad, enough to reach the AFC title game for a second time in three seasons, and the Broncos hope it will be enough to overcome Brady, Belichick & Co. when the Patriots travel to Denver for a matchup between the AFC’s top two seeds.

“We have tons of confidence in Peyton,” Broncos cornerback Chris Harris Jr. said. “He did the job we needed him to do.”

Manning was steady Sunday but far from spectacular. The offense couldn’t extend drives, and the Broncos trailed for much of the game. Plus, the wind was swirling and Manning’s teammates dropped several passes. As they have much of the season, the Broncos had to look to their stellar defense to turn in a big play when it was needed most.

Five minutes into the fourth quarter, the Steelers held a 13-12 advantage. That’s when Pittsburgh running back Fitzgerald Toussaint took a handoff and was met by Broncos cornerback Bradley Roby, who popped the ball loose. Denver recovered and took over on its 35-yard line, putting momentum, at least for the moment, at the Broncos’ backs.

“When we got into the huddle, Peyton said, ‘We gotta get seven here,’ ” Denver tight end Virgil Green said, “and everybody bought in.”

At first, it looked like so many of the day’s offensive drives: A holding penalty negated a big gain, and Manning threw a near-interception. But the Broncos were workman-like, if not overwhelming. Manning hit wide receiver Bennie Fowler for a 31-yard gain, and Denver took to the ground, inching toward the goal line. C.J. Anderson finally punched in a one-yard touchdown with three minutes remaining in the game to give the Broncos the lead.

Denver converted the two-point conversion and later added a field goal — Brandon McManus’s fifth of the day — with just 53 seconds remaining in the fourth.

Manning finished the game with 222 yards on 21-for-37 passing. He had no touchdowns but, most importantly, no interceptions, either.

“He put us in some great plays,” Anderson said. “He saw blitzes coming. We kept him clean for most of the game. So if we can do that, we always have a chance.”

Even if Manning can’t physically perform as he once did, however, Steelers players said the veteran quarterback still poses problems. “It’s just an above-the-neck game,” linebacker James Harrison said. “He’s seen it all and heard it all.”

Manning evidently played capably enough, too, to keep backup Brock Osweiler on the sideline, although it may not have been the type of highlight-filled performance that has heralded past Manning-Brady matchups.

Yes, the Broncos stopped a Pittsburgh team that was trying to avenge a 2012 overtime playoff loss in the same stadium. But this was an ailing Steelers group. The star wide receiver (Antonio Brown) was sidelined with a concussion, the starting running back (Toussaint) began the year on the practice squad and quarterback Ben Roethlisberger took the field with a throwing arm akin to an overcooked noodle.

Roethlisberger was listed as questionable on the injury report after suffering a right shoulder separation and ligament damage against the Bengals one week earlier. But he still came out firing Sunday, finishing the game with 339 yards on 24-for-37 passing.

The Broncos now will graduate from the Steelers to a buzzsaw. The Patriots lost to the Broncos, 30-24, in overtime on Nov. 29 and are surely licking their chops to face the Denver offense once more. Manning missed their regular season matchup because of injury and didn’t regain the starting job from Osweiler until the regular season finale.

Manning has topped Brady just once since 2009 and trails the all-time series 11-5. Manning has won two of their three previous meetings in AFC championship games.

Following Sunday’s win, Manning was certainly aware of the duel that looms, but he wasn’t ready to delve too deeply into the quarterback saga that is to come. In his postgame news conference, he didn’t utter Brady’s name once.

“We’ll deal with that one Wednesday,” Manning said. “We have a couple of hours to enjoy this one tonight.