ST. LOUIS – Mark McGwire's balky right knee has landed him back on the disabled list.

	Mark McGwire can only watch his St. Louis Cardinals for at least the next 15 days, and likely longer, because of his knee injury.

The St. Louis Cardinals first baseman, limited to six games this season, is still recovering from offseason surgery to correct tendinitis, and the team believes he pushed himself too much.

The move to the 15-day DL made on Wednesday was backdated to Monday, but he could be out a lot longer.

"The figure I'd pick out is longer than 15 days," manager Tony La Russa said before the Cardinals played the Arizona Diamondbacks. "It's hard to believe in 15 days he would be ready for this."

It's been six months since McGwire underwent surgery. Cardinals doctors say the quickest recovery for an athlete from similar surgery is six months for NBA player Alonzo Mourning. La Russa said others have required 11 and 12 months.

McGwire played more than expected in spring training, partly because he was feeling good and partly because he wanted to get as many at-bats as possible to shake off rust. La Russa said he doesn't second-guess himself for letting McGwire play too much, too soon.

"I regret the fact that he's not available, but I really don't regret the way he was played," La Russa said. "There wasn't one time that he played that anybody was careless.

"It was discussed, it was planned. There were days he felt great and came out after two at-bats."

McGwire, baseball's single-season home run king with 70 in 1998, has been bothered by the knee since last season. He had just 15 at-bats after the All-Star break because of the sore knee and couldn't play in the field.

This year he's 2-for-21 (.095) with one home run, the 555th of his career.

"All I know is, I'm not myself," McGwire said Tuesday. "I have to play at a certain level and I'm not there. If I don't play at a certain level, I think I'm embarrassing myself and I'm no good to a ballclub."

La Russa is confident McGwire will be back, sooner or later.

"This is April, and I'm hopeful that he'll get back with a lot of season left," La Russa said. "These guys, when they heal, they heal 100 percent."

McGwire declined to talk to reporters before the game Wednesday.

Bobby Bonilla and Eli Marrero will get the bulk of time at first base while McGwire is out. Entering Wednesday's game, Cardinals first basemen were a collective 9-for-55 with three RBI -- one each from McGwire, Bonilla and Marrero.

Bonilla, 38, started at first base Wednesday, but La Russa said he didn't think he could play every day at this stage of his career. La Russa said he also could use rookie Albert Pujols, who entered the game batting .400 and with an 11-game hitting streak, at first.

The Cardinals also optioned pitcher Chad Hutchinson to Triple-A Memphis and called up outfielder Kerry Robinson and pitcher Jason Karnuth. Hutchinson has a 24.75 ERA, allowing 11 runs in four innings, and his struggles are partly related to inactivity. He went 10 days between his first and second appearances.

Hutchinson, a second-round draft pick in the 1998 draft, will be a starter at Triple-A Memphis.