Except it wasn’t that simple.

Seattle’s defense was stouter than expected with defensive tackles Colin Cole and Brandon Mebane holding their ground, leaving linebacker Lofa Tatupu free to clean up the mess. Heck, even cornerback Kelly Jennings with a critical open-field stop of Gore, who outweighs him by nearly 40 pounds.

Gore gained only 38 yards on 17 carries in the game as Seattle’s defense is the only reason the Seahawks stayed in Sunday’s game. They gave up just six points even though the 49ers drove inside the Seattle 10 on each of their first three possessions.

The run defense was one of the only bright spots of this team last season. Seahawks allowed only two players to surpass 100 yards rushing against them last season, quite an accomplishment considering how lopsided so many of Seattle’s losses were. Judging from Sunday, the run defense may be even better this season.

San Francisco cornerback Nate Clements was working off that scouting report, aggressively looking to jump routes. It paid off on Seattle’s first possession when Clements totally disregarded Deion Branch — the player Clements was supposed to be covering — to jump in front of tight end John Carlson for an interception.

It cost the 49ers in the second quarter both on Mike Williams’ 35-yard reception to set up Seattle’s first touchdown and on Deon Butler’s 13-yard touchdown reception that put the Seahawks ahead 14-6 at halftime. In each instance, Seattle caught Clements creeping forward, biting on the wide receiver’s first move and leaving the defense vulnerable when the route continued after that.

The only sign of progress on the ground was the fourth-quarter field-goal drive in which Seattle ran the ball eight times, using three different backs, gained 48 yards and two first downs and put Seattle in position for the final score.

Defensive end Red Bryant had the first sack of his NFL career in the first half while defensive end Chris Clemons consistently pressured Smith in the second half. The Seahawks were a little over-eager with three penalties for neutral-zone infractions, but Seattle’s ability to pressure the passer — a consistent problem last season — showed signs of improvement.

And when Smith had a chance to put San Francisco ahead in the second quarter on a fourth-and-1 play at the Seattle 6, he lobbed a pass toward fullback Moran Norris and watched his fullback make a painfully awkward attempt to spin and catch the football. The ball looked like it was 6 feet over Norris’ head. It wasn’t or at least it shouldn’t have been if Norris turns like you’d expect person who’s paid to play sports would be able to. But ultimately it’s the quarterback’s job to put his team in position to succeed, and that means knowing your personnel. The pass to Norris was so wide open, which made it that much more awkward to watch it fail.

The 49ers did not plan to rely on Smith to beat Seattle with his arm, and when the Seahawks jumped out in front and the 49ers had to start throwing, they were dead in the water.