DENVER — Now that they're teammates, Peyton Manning can celebrate when Tracy Porter returns an interception for a touchdown.

Three seasons ago Porter denied Manning a second Super Bowl title when he returned an interception 74 yards to seal the New Orleans Saints' win over the Indianapolis Colts.

Their Denver debut Sunday night was a success thanks to Manning's magnificent return from a year's absence and Porter's 43-yard interception return for a score that sealed their 31-19 win over the Pittsburgh Steelers.

The Broncos' final drive stalled at the Steelers 8 and Matt Prater's short field goal left Roethlisberger with 3 minutes to erase a 25-19 deficit.

"We wanted to get a touchdown there at the end and it was frustrating to have to settle for a field goal," Manning said. "Hate to give Roethlisberger a chance in the two-minute drill."

Roethlisberger had gone a great job matching Manning's mastery of the no-huddle and keeping the four-time MVP on the sideline much of the night by converting 11 of 19 third downs.

After a 19-yard completion to his 39, Roethlisberger threw an incomplete pass, then tried to thread a pass to receiver Emmanuel Sanders along the left sideline.

Porter, who also had eight tackles and broke up five passes — the most by a Denver defender in 11 seasons — stepped in front and took it to the house.

"There's a safety over the top so I'm aggressive on anything short," Porter said. "The quarterback tried to fit it in there and I just made a play on the ball. Any defensive back playing opposite Champ (Bailey) is going to get the work. I just made the most of my opportunity."

"I should've called timeout," Roethlisberger said. "The play clock was running down, I hate to burn timeouts. I should've. We were kind of all over the place.

"There's no one to blame but myself. I already told my teammates and coaches that it's my fault. It's on me. It's disappointing. I hate to let my team down, my coaches, the fans. That loss is squarely on my shoulders. I'll take that and get better and learn from it."

After 1 year, 8 months and 2 days away from the game, Manning couldn't wait to resume his career, but Roethlisberger was determined to keep him on the sideline, giving the Steelers more than a 10-minute advantage in time of possession.

Whenever he was between the lines, Manning was masterful, finishing with a 129.2 passer rating.

The four-time MVP coming off four neck surgeries that wiped out his final season in Indianapolis last year completed 19 of 26 passes for 253 yards and two touchdowns. He was sacked twice and bounced up both times without trouble.

Manning, jettisoned by the Colts in March after missing all of last season with a nerve injury that weakened his throwing arm, took just two snaps in the third quarter. But one was a 71-yard touchdown throw to Demaryius Thomas, Manning's first as a Bronco and the 400th of his career.

He reached the milestone in his 208th career game. Dan Marino did it in his 227th game and Brett Favre in his 228th.

"It's an individual record but I accept it on behalf of many great teammates and coaches," Manning said. "Dan Marino and Brett Favre are two of my favorite players of all time, two of the best quarterbacks of all time. I don't really feel comfortable being in that company, but to be mentioned among them, it's truly humbling and quite an honor."

Manning, however, didn't even keep the ball for his trophy case.

"I talked to him after the game and said, 'You're going to let me keep the ball right?' He got one of the game balls, so he gave me that ball," Thomas said. "That's great to be able to catch his 400th. Hopefully he'll sign it for me. I can go back and show my grandkids in the record book."

Manning, who hadn't played in a game that counted since Jan. 8, 2011, spent much of his night on the sideline as Roethlisberger led a clock-chewing offense that had Denver's defenders gassed and Manning antsy as the Steelers converted 11 of 19 third downs.

"Roethlisberger was awesome on third down," Manning said. "I've seen that before throughout his career. He does a good job extending plays. You get up to warm up, kind of getting ready and see them on a third-and-15 and thinking you're about to go out there and he converts it and you go back and sit down. We thought it was important when we got the ball back we had to be efficient."

At one point, Roethlisberger had taken 30 snaps to Manning's one — a kneel-down — during two monstrous drives that spanned halftime.

"Roethlisberger was awesome on third down," Manning said. "Wasn't much fun sitting on the bench there all night. Great job by our defense in the end, getting that turnover."

After going to the no-huddle midway through the first half, Manning led Denver on three straight 80-yard touchdown drives, picking apart Pittsburgh's defense with precision.

"It helped a lot," Manning said of the hurry-up. "We're going to use the no-huddle as a change-up. Once we did it, it went so well, the coaches kind of said stay with it. I was kind of afraid that might happen."

After Porter's pick-six, Roethlisberger was sacked three times on his last possession after going down just twice all night.

"Better late than never," said Von Miller, who had two of those sacks.

Although this one was a screen pass, Thomas' long TD was reminiscent of his 80-yard touchdown on a crossing pattern on the first play of overtime that beat the Steelers 29-23 in the AFC wild-card game eight months ago when Denver was Tim Tebow's turf.

That changed when Manning was released by the Colts on March 7 after 14 seasons and after a frenzied free agency tour chose Denver as his destination for his comeback two weeks later. The Broncos sent Tebow to Broadway 24 hours later.

On Sunday night, Manning looked like he hadn't missed a beat — or 611 days.

"What can you say?" Steelers safety Troy Polamalu said. "I mean, he's Peyton Manning. He's the same Manning. Everything anybody has ever said about him is probably the same thing I would say tonight."

NOTES: Denver DT Ty Warren, playing in his first game since 2009, sprained an elbow in the first half and didn't return. ... Also hurt in the first half were Steelers O-linemen Marcus Gilbert (knee) and Ramon Foster (eye). ... Steelers star LB James Harrison (knee) sat out, as did S Ryan Clark, who has sickle cell trait that makes playing at altitude dangerous.