Ben Roethlisberger threw for two touchdowns and Rashard Mendenhall added the first two rushing scores of his career as the Steelers rebounded ended their losing streak at two games and evened their record at 2-2, one game behind Baltimore and Cincinnati in the AFC North standings.
San Diego, which lost to the Steelers for the third time in less than a year, falls to 2-2. It was the kind of offensive output that was expected from the defending Super Bowl champions this season.
Mendenhall, making his second career start in place of Willie Parker, had a monster game, carrying the ball 29 times for 165 yards and two touchdowns. He also caught two passes for 26 yards.
It was a perhaps career-changing performance for a player who entered the game with 103 career rushing yards and was so lost in practice last week that head coach Mike Tomlin chose not to use him on offense during a 23-20 loss at Cincinnati last week.
"He played a good game," said Tomlin. "He had a good week of practice. I'm not going to take any credit for that. I didn't rush for a yard. He did a nice job."
Mendenhall was hardly the only star for the Steelers.
Roethlisberger continued his hot start to this season, completing 26 of 33 passes for 333 yards and two touchdowns. He has now thrown for at least 275 yards in three of the Steelers' four games this season.
Linebacker James Harrison added a pair of sacks, including a sack-strip on San Diego's final play from scrimmage.
The Steelers established their dominance on the opening possession of the game, going 79 yards on just six plays – three passes, three runs – to score on Mendenhall's first touchdown, a one-yard run.
After forcing the Chargers to punt after running just three plays, the Steelers against methodically marched down the field, this time on 11 plays, capping a 75-yard drive on a 19-yard touchdown pass from Roethlisberger to running back Mewelde Moore.
Things didn't get much better for the Chargers in the second quarter, as the Steelers added a two-yard touchdown run by Mendenhall with 1:33 remaining in the first half to take a 21-0 lead into the locker room.
Pittsburgh held a 274-72 advantage in total yards and 19-4 edge in first downs in the first half. The Steelers finished with a 497-251 advantage in total yards.
The Steelers added a second Roethlisberger touchdown pass, this one a six-yarder Miller, on their first possession of the second half to go ahead 28-0 before the Chargers finally showed some signs of life.
Philip Rivers tossed a three-yard TD pass to tight end Antonio Gates, and fullback Jacob Hester took the ball off the Steelers' Stefan Logan on a punt return as Logan fought for extra yardage, returning it 41 yards for a touchdown with 12:37 left in the game to trim Pittsburgh's lead to 28-14.
A 32-yard run by Mendenhall on the Steelers' next possession and a six-yard halfback option pass for a touchdown from Moore to Miller before Rivers and Gates connected for a second touchdown pass, this one from 30 yards, to make it 35-21 with 5:48 remaining.
Rivers then threw a 13-yard TD pass to Chris Chambers after the Chargers recovered an onside kick to make it 35-28 with 4:31 left in the game. But the Steelers used a clock-draining drive to set up a 46-yard Jeff Reed field goal with 43 seconds remaining to close out the game.