KANSAS CITY, Mo. -- The Kansas City Chiefs' beleaguered defense took another blow Wednesday when linebacker Lew Bush was suspended for four games after testing positive for a banned substance.

The Chiefs said the action was taken after a routine test by the league, which ordered the suspension because of a violation of its "anabolic steroid and substance policy.''

A 10-year veteran, Bush had lost his job to rookie Scott Fujita. For this week's game at San Francisco, his place as backup outside linebacker will be taken by Glenn Cadrez.

Although he was no longer starting, losing Bush for four games is a setback for a defense that's been struggling to escape the NFL's statistical cellar. While the offense has been among the best during the first half of the season, the defense has ranked 32nd -- dead last -- in total defense, pass defense and scoring defense.

Bush will be eligible to return after the Chiefs play the Arizona Cardinals on Dec. 1.

Coach Dick Vermeil said league policy prohibited him from saying much about the situation. League rules dictate Bush be removed from the organization entirely for four games.

"No comment other than I'm very sorry and feel very bad for the young man,'' Vermeil said. "That doesn't mean I can't talk to him on the phone and make sure he's doing all right."

Bush's spot on the 53-man roster was filled by wide receiver Marvin "Snoop'' Minnis, activated for the first time since breaking a bone in his right foot during a workout in May. Minnis probably will not be active for this week's game at San Francisco.

In a 20-10 victory over Oakland in their previous game, the Chiefs still gave up over 400 yards but believed they showed improvement by only yielding one touchdown.

"I've said all along I see different things improving within the scheme, and how we play and the people who play the positions,'' Vermeil said.

His players and coaches do not worry about being ranked No. 32 even though the media has dubbed them "The 32 defense.''

"Within our team confines, we do not talk about where we rank,'' Vermeil said. "We rank 4-4. That's where we rank.''

In the 49ers, with quarterback Jeff Garcia and wide receiver Terrell Owens, the Chiefs might be facing their most potent offensive opponent this season.

"You've got to go out with a good game plan and try to contain him and Garcia both,'' cornerback Eric Warfield said. "Those are two guys who can really hurt you.''