SAN FRANCISCO -- The 49ers offense couldn't afford to be normal. Nickel-and-diming wasn't going to be enough. Apparently that truth was not lost on San Francisco's play-callers.

Phil Dawson made the game-winner. Frank Gore was the hero. The defense was the defense. But the difference in Sunday's 19-17 critical home win over Seattle was Jim Harbaugh and offensive coordinator Greg Roman shedding some of their conservative tendencies.

They didn't exactly take the handcuffs off. But they certainly loosened them enough to open up some things on offense. With pride on the line, facing a team that's owned them the last two meetings, the 49ers became more assertive on offense.

About. Time.

"I thought we were," Harbaugh said. "I thought we were aggressive."

That's the necessary mindset when you're in the 49ers' position. San Francisco (9-4) already has lost whatever it could be trying to preserve -- the division crown, home-field advantage, aura as an NFC power -- with a conservative offense. You don't win tough, December football games playing timidly. The George McFly approach won't cut it.

Especially with all the weapons back, they've got to be takers. And they were Sunday, for the most part. Definitely more than they have been in the past.

Sure, several moments throughout the game reeked of same ol' Niners. But when playoff hopes hung in the balance, when yards had to be gobbled up, the brain trust erred on the side of let's-go-take-it.

This wasn't going to be one of those games the 49ers defense could win despite the offense. Seattle (11-2) is too good. The 49ers were going to have to move the ball, put some points on the board, win time of possession. And that was going to take some doing from the game-planners.

An assist goes to the staff for opening up the playbook, especially in the first half. They stretched out the Seahawks defense. They used the whole field. They ran sweeps and play-actions and designed running plays for Colin Kaepernick and wide receiver picks and took shots down field. It was a welcomed sight for 49ers fans who have grown tired of three-and-out parades.

"The offense was open," Gore, who had his first 100-yard game since Week 6, said with a smile. "We used just about everything."

It was the kind of creativity and versatility needed to break the spell the Seahawks defense had on the 49ers offense. The 49ers walked away with 318 yards against a Seahawks defense that had held opponents to a league-low 284 yards. The 49ers' 19 first downs Sunday were two above their average.

And the last two were the most important.

After Seattle took advantage of a short field and converted the go-ahead field goal, the 49ers found themselves in desperate need of a scoring drive. On first down at their own 31, with 4:21 left in the game, the 49ers dialed up a perfect call.

They didn't ram Gore into the line and prays he squeezes through. They pulled out a pulling, sweeping special, putting Gore in space with blockers ahead of him, taking advantage of his great vision and interior quickness.

Gore broke it for 51 yards.

"G-Ro had been saving that call in his back pocket and picked the exact right time to call it," Harbaugh said after the game. "And Frank executed it."

It looked as if the 49ers, in position for the go-ahead score, were about to go all conservative and set up Dawson for the game winner. Back-to-back runs to nowhere had the 49ers facing a difficult third down against a Seattle defense fighting for its life. You just knew they were going to run it in the middle, get it to the center of the field, settle for the field goal.

This has been the 49ers offense most of the year. Keeping it simple. Protecting the ball.

Small problem: More than three minutes remained on the clock.

But on this day, the play-callers were game. Harbaugh and Roman decided to go for the first down and eat more clock. Quarterback sweep to the left. Kaepernick picked up the crucial first down on the same play, per Joe Staley, that paved the way for Alex Smith's TD run in the playoff shootout against the Saints two seasons ago.

The 49ers didn't score a touchdown this time. They ended up with a game-winning field goal. But point is, they went for the gusto on that third-down call.

San Francisco fans can only hope this is the beginning. As Anquan Boldin said, every game is a playoff game from here on out. That's the kind of urgency the 49ers are playing with. They will need the same from the play-callers.

Contact Marcus Thompson at mthomps2@bayareanewsgroup.com. Follow him on Twitter at twitter.com/ThompsonScribe.