RENTON, Wash. - The play came in the opening moments of the first quarter and spoke to the determination of Seattle's defense.

On a third down inside the Seattle 10, 49ers running back Frank Gore caught a short swing pass out of the backfield. Gore, a longtime battering ram nemesis of the Seahawks, had only slender, 180-pound cornerback Kelly Jennings to beat for a first down or potential touchdown.

Jennings wouldn't let that happen. He chopped down Gore for just a 1-yard gain.

"I've been the small guy all the time and tackling is something else I've been working on just talking to the coaches about improving on," Jennings said.

For all the hype around Pete Carroll's successful debut in his return to professional football, one aspect got overshadowed on Sunday: Seattle's defense played pretty well.

Gore, who was averaging nearly 150 yards rushing per game against Seattle since the 2006 season, was held to a pedestrian 38 yards on 17 carries. This was the same player who twice in his career has rushed for more than 200 yards against Seattle.

After tormenting the Seahawks in the past, Gore being bottled up was a big reason why the 49ers offense never got started.

"Frank, he found some holes in some cases, he found the crease and he's a great athlete. He's made us miss on some tackles," Seattle linebacker Lofa Tatupu said. "I think that's what we shored up. Maybe one guy would miss, but the next two weren't going to miss."

Seattle's run defense, and specifically its defensive line, was a major question entering the season. The Seahawks had shifted Red Bryant from tackle to defensive end in the hopes of being more stout at the line of scrimmage with Bryant, and defensive tackles Brandon Mebane and Colin Cole plugging the run lanes.

Carroll raved about Cole's effort on Sunday and had almost as much praise for newcomer Junior Siavii. Signed only a week ago, Siavii played extensively and finished with two stops and a tackle for loss.

The Seahawks clogged run lanes with just their base defense and forced San Francisco to face third-and-5 or longer 11 times.

The 49ers finished just 1 for 15 on third-down conversions.

That put more pressure on 49ers quarterback Alex Smith, who tossed two interceptions - both on third downs - with the second of his two turnovers returned 32 yards for a touchdown by Seattle cornerback Marcus Trufant.

Seattle's defense might only get better this week heading into Denver with the expected return of linebacker Leroy Hill. Carroll said Monday that Hill will rejoin the team after serving a one-game suspension handed down by the league for his arrest on a marijuana-possession charge in Georgia. He began 12 months of probation for that in April.

Hill could have faced an additional suspension after he was arrested on a domestic violence charge in the Seattle suburb of Issaquah in April. The 27-year-old Hill entered into a stipulated order of continuance at a hearing on his misdemeanor charge of fourth degree assault/domestic violence on Aug. 19. Prosecutors said Hill is essentially on probation for 18 months and must complete a one-year state-certified domestic violence treatment program - 26 weeks of weekly therapy and counseling, then monthly sessions for six months - plus 25 hours of community service.

Carroll said Hill won't start, but will play against Denver.

"We're pleased to have him back and we're going to get him to play," Carroll said. "He's not coming back to sit, he's coming back to play."