SANTA CLARA, Calif. (AP) - The San Francisco 49ers are achieving their goal of fielding a top NFL defense, but ringleader Patrick Willis and his crew are far from satisfied with the results two weeks into the season.
The All-Pro linebacker is off to a typically strong start and his teammates have played well around him. But the defense hasn't played quite well enough to lead San Francisco to its first victory. The 49ers (0-2) face the undefeated Kansas City Chiefs on Sunday.
"It hasn't been perfect, but for the most part we've been OK," Willis said Thursday. "But there's been some errors on our part, too. We can be a lot better."
The 49ers were pretty good Monday night against New Orleans and the league's No. 1 offense. The Saints managed just 231 yards entering the final minute before driving to the winning field goal.
The Saints had to rely on reigning NFL passing champion Drew Brees to take them down the field because the 49ers stuffed them on the ground. New Orleans averaged 2.1 yards per carry and had just one first down rushing.
That has been typical of the 49ers, who have become one of the league's toughest teams to run against. San Francisco is allowing just 63.5 yards on the ground.
The 49ers will need to set the tone again with their rushing defense against the Chiefs, who have started with two victories primarily because of what their offense has done on the ground.
Halfbacks Jamaal Charles and Thomas Jones have combined for 263 yards rushing for the league's fifth-ranked rushing attack. They've carried an offense that ranks 30th in the NFL overall.
Each rushed for more than 1,000 yards last season, and they'll be running this week into the heart of a San Francisco defense looking to prevent the 49ers' first 0-3 start since 2004.
"Every week our defense prides itself on trying to stop the run first," Willis said. "They have speed and power back there, but it's going to be a game. We're going to go out and play our football."
Willis, the NFL's leading tackler two of the past three seasons, is on a similar pace this year with 21 tackles through two games. He again is thriving behind nose tackle Aubrayo Franklin, who ties up blockers in the middle of San Francisco's 3-4 defensive scheme so Willis and fellow inside linebacker Takeo Spikes can roam free and make plays.
Franklin, designated as San Francisco's franchise player in March, didn't join the 49ers until the end of August this year after missing all offseason team workouts while he sought a new contract. But Franklin has made up for lost time since his return.
"I've knocked the rust off and I'm back in there now," said Franklin, who had a career season last year with 88 tackles. "It's just like where we left off last year. We're playing off each other and everything and playing within the scheme. We haven't allowed much rushing, but we haven't won a game yet either. So I can't brag on that."
The 49ers may have a new starter next to Willis on Sunday. Spikes left the Saints game in the second half with a knee contusion and did not return after making five tackles. Spikes did not practice Wednesday or Thursday and his status for the Chiefs is uncertain.
San Francisco got a lift from rookie NaVorro Bowman, who filled the void left by Spikes by contributing five tackles and aggressive play. There was no drop in performance when Bowman entered the game, and the third-round draft pick has worked with the first unit in practice this week.
The 49ers currently have no other inside linebackers on their roster.
"I'm confident and ready to go and I want to show these veterans that this young guy can really step up and do what I have to do," Bowman said. "They take a lot of pride in the run defense here, and I believe I can fit in and do a lot of things to help this team win."