DENVER (AP) -- Peyton Manning made a successful NFL return from a year's sabbatical, leading the Broncos past the Pittsburgh Steelers 31-19 in his Denver debut Sunday night.
The four-time MVP coming off four neck surgeries completed 19 of 26 passes for 253 yards and two touchdowns.
He got a big assist from another free agent, cornerback Tracy Porter , whose 43-yard interception return of Ben Roethlisberger 's pass with 2 minutes left sealed the win.
Manning, jettisoned by the Indianapolis 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.
Manning reached the milestone in his 208th career game. Dan Marino did it in his 227th game and Brett Favre in his 228th.
Manning spent much of his night on the sideline as Roethlisberger led a clock-chewing offense that had the ball for 10 minutes longer than Denver did. 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 of Pittsburgh's 11-of-19 conversion rate. "Wasn't much fun sitting on the bench there all night. Great job by our defense in the end, getting that turnover."
When he was between the lines, Manning was masterful.
He led Denver on three straight 80-yard touchdown drives and had the Broncos at the Steelers 8 when his next drive stalled and they settled for Matt Prater 's short field goal and a 25-19 lead with 3 minutes left.
Porter stepped in front of Emmanuel Sanders and returned an interception 43 yards for the score a minute later, and Roethlisberger was sacked three times on his last possession after going down just twice all night.
Coach John Fox called Porter's pick "the biggest play of the game."
The Steelers converted some very long third downs as Denver's defense grew fatigued.
Manning was sacked twice and both times bounced right up with no issues.