San Francisco ? Antonio Pierce found out just how easy it has become to beat the San Francisco 49ers: Simply stand in one place and allow their mistakes to find you.

The Washington linebacker got his first NFL touchdown on an interception thrown by Ken Dorsey, who hit Pierce between the numbers deep in Redskins territory with 48 seconds left in the first half.

Pierce returned it 78 yards for a score in a 26-16 victory Saturday. Though the Redskins committed many of the same penalties, mistakes and lapses that have plagued their season, he realizes Washington’s problems pale in comparison to San Francisco’s woes.

“San Francisco, they’re going to improve in the future, but we felt this was a game we should have, no excuses,” said Pierce, who had the biggest of Washington’s four interceptions. “It was 78 yards to the end zone? I knew there was a reason I was tired.”

Patrick Ramsey passed for 214 yards and a touchdown, Clinton Portis rushed for 110 yards, and Rod Gardner caught six passes for 111 yards — but the Redskins (5-9) were disappointed in their offense, which scored its only touchdown on the opening drive.

“We had an opportunity to lose that game if our defense didn’t play so well,” Ramsey said. “(The offense is) contributing more, but not as much as we would like. We’ve just got to get the ball in the end zone.”

Washington also committed 11 penalties for 93 yards to stay on pace to break the franchise record. Without newcomer Jeff Chandler, who kicked four field goals, the Redskins’ task would have been much tougher.

But when teams face San Francisco (2-12), they’ve got plenty of margin for all sorts of errors.

“The thing that I am proudest of is just the way they fight,” Redskins coach Joe Gibbs said. “I think our guys fight hard every week, and sometimes things are not that pretty. We just fought and played hard.”

The Redskins took a 19-point lead late in the first half, and the defense shut out the Niners’ offense for more than 45 minutes between Brandon Lloyd’s early TD catch and Curtis Conway’s scoring grab with 4:26 left.

Dorsey, making his fifth start in place of injured Tim Rattay, doubled his interception total for the season, including three in the first half. He finished 20-of-38 for 206 yards.