The four-time MVP coming off four neck surgeries completed 19 of 26 passes for 253 yards and two touchdowns.
Manning, jettisoned by the Indianapolis Colts in March after missing all of last season with a nerve injury that weakened his throwing arm, hit Demaryius Thomas with a 71-yard touchdown toss for his first score as a Bronco. It was his 400th career TD toss.
Through three quarters, Manning was 12 of 16 for 178 yards.
The Steelers looked as if they had regained the lead with 24 seconds left in the third quarter when Jonathan Dwyer scampered in from 11 yards. But after review it was ruled his knee touched the field at the 2 late in the quarter.
Ben Roethlisberger and the Steelers’ offense have been highly proficient, especially on third downs as they converted 11 of 16 chances. But they’ve struggled to get the ball into the end zone, settling for two field goals by Shaun Suisham.
Just before halftime, Roethlisberger found his tight end Heath Miller over the middle and Miller simply walked into the end zone for a 4-yard score with 28 seconds remaining in the half. The Steelers converted on four third downs during the 14-play scoring drive.
Earlier in the second quarter, Denver’s Knowshon Moreno bounced outside for a 7-yard TD run. Manning was magnificent on Denver’s scoring drive, completing 6 of 7 passes for 54 yards. He also flashed some speed as he scrambled away from pressure and ran for 7 yards.
Moreno made a nifty cut on his surgically repaired right knee, juking Pittsburgh defenders before bounding into the end zone. Moreno missed a good chunk of last season after tearing his ACL at Kansas City.