SANTA CLARA, Calif. -- The key to a successful offensive game plan for a first-time starting quarterback is generally simple enough.

Run the ball.

With quarterback Mason Rudolph starting for the first time, the Pittsburgh Steelers entered Sunday’s game against the San Francisco 49ers with the intention of leaning on third-year running back James Conner.

The 49ers loaded the box early and often with eight defenders, trying to force Rudolph to throw. Pittsburgh, however, couldn’t get anything going in the passing game, settling for short throws barely past the line of scrimmage. And with the 49ers’ stacked front, the Steelers couldn’t run the ball effectively, either, creating a lackluster offense in Rudolph’s starting debut.

Conner ran the ball just once on the first two drives before opening up the third drive with back-to-back carries. He got the ball once more on the drive, one that ended in a punt just before halftime. That capped off a half in which he carried the ball seven times for 18 yards. His longest run went for just 5 yards.

It wasn’t until the fourth quarter that Conner finally had a double-digit run, picking up 10 yards to open a drive that ended with Rudolph’s 39-yard touchdown pass to Diontae Johnson.

It was the kind of run the Steelers needed from Conner all afternoon but got just once.

When his number was called again in the fourth quarter to milk the clock after the 49ers’ fifth turnover, Conner ran for 5 yards and then fumbled it away two plays later, giving the 49ers the ball just outside the red zone.

“That never happens to James,” Rudolph said of the fumble. “James is an unbelievable player. We were still being aggressive in that situation and mixed the run with the pass.”

Those were Conner’s final three carries of the afternoon, and the only three carries of the fourth quarter.

Conner finished the game with 45 yards on 13 carries -- the most he’s had this season. But it’s a far cry from his standard a season ago.

Last season, he had only three games in which he carried the ball fewer than 13 times, and the Steelers went 1-2 in those games. The Steelers were 7-2-1 last year when Connor rushed at least 13 times.

Through three games this season, Conner is averaging an anemic 2.9 yards per carry. He has rushed just 34 times for 97 yards -- far from his numbers through three games a season ago. In the 2018 three-game opening stretch, Conner rushed for 213 yards on 54 carries and scored three touchdowns. He has just one this season.

Part of the problem, of course, is that the Steelers went away from the run game when trailing 20-0 to the Patriots in Week 1. And even before Pittsburgh found itself in a three-score hole in that game, the run game was hardly effective. Offensive coordinator Randy Fichtner tried to lean on Conner to pick up a third-and-1 early in the game, calling an inside run that was snuffed out before the line of scrimmage. That influenced his subsequent calls, he said, and caused him to go away from the run.

“I think we ran it 10 times in the first half,” Fichtner said. “It probably wasn’t as efficient per run. I probably got a little bit down when we didn’t make the first third-and-1. ... We didn’t get it, and it probably drained on me for the next several calls that I made.”

Conner also isn’t getting long runs off this season. Last year, his longest rushes in the first three weeks went for 22 and 27 yards. This year, he’s had a 14-yarder to go with Sunday’s 10-yard run.

So far, the Steelers’ longest rush of the season belongs to rookie Benny Snell, who picked up a 23-yard gain against the Seahawks a week ago. The Steelers have also expressed plans for Jaylen Samuels as a pass-catcher out of the backfield, but he didn’t get on the field Sunday.

The Steelers know how to manufacture a dominant run game. They did it a season ago with Conner as Le’Veon Bell held out. This year, though, second-guessing and an inexplicable lack of commitment to the run is dramatically hurting the offense.

“You got to trust yourself,” Fichtner said in the week after the loss to the Patriots. “You got to trust your preparation. You’re going to maybe get beat at the point of attack and not make one or make a bad cut and not get one, but it doesn’t necessarily mean that the scheme is bad and the opportunity next time won’t be good. I think you just got to stick to your guns and the type of things you do.”