Trace Armstrong and the Dolphins put the clamps on Jon Kitna's Seahawks.

But when the Dolphins stepped into the playoff spotlight, their defense was ready to shine. Miami allowed a season-low 171 yards in Sunday's 20-17 victory at Seattle.

The performance bolstered the confidence of a team that started 7-1, then slumped and barely made the playoffs. Miami advances to a second-round game Saturday at Jacksonville.

"We're back on the right track," said defensive end Trace Armstrong, who set a team playoff record with three of Miami's six sacks against the Seahawks.

The victory was reminiscent of a stretch at midseason when the Dolphins defense went 16 consecutive quarters without allowing a touchdown.

"I have no clue as to how they were able to push us around like they did," said Seahawks running back Ricky Watters, who was limited to 40 yards on 19 carries. "They controlled us and really handled us. They made us look pretty bad."

In the second half, Seattle gained just 32 yards on 23 plays. Miami tackles Daryl Gardener and Tim Bowens plugged the middle and helped harry quarterback Jon Kitna.

"It's one thing when you have guys that can rush hard from the end," Kitna said. "But they have two huge guys in the middle, too, with Gardener and Bowens. Those guys get some push up front, so as a quarterback there's nowhere to move."

Because of the much-publicized feud between Dan Marino and coach Jimmy Johnson, speculation about their possible retirements and Miami's 1-5 finish, the defense has been overlooked much of this season. The Dolphins ranked fifth in the NFL in yardage allowed.

The defenders contributed to a December nosedive by giving up too many big plays and blowing second-half leads in two losses, but there were no breakdowns Sunday. Seattle's longest gain was 22 yards, and when the Dolphins took their first lead with five minutes left, the front four swarmed Kitna to close out the victory.

The Dolphins won the same way they did early in the season, employing a conservative, error-free, ball-control offense. Marino handed off more than he passed for the first time since mid-November, and Seattle had the ball for only 25 minutes.

"By not turning the ball over and running the ball well, the offense helped us a lot," Miami All-Pro linebacker Zach Thomas said.

Jacksonville, which boasts the NFL's top-ranked rushing attack, poses a more formidable challenge. But the Dolphins overcame a 3,000-mile trip for their first road playoff victory in 26 seasons, and they headed back to Miami with a sense of momentum.

"What we're trying to do is snowball," receiver Oronde Gadsden said.