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04/15/09 3:26 PM ET

Cardinals place Carpenter on DL

Rib-cage strain sidelines hard-luck ace four to eight weeks

PHOENIX -- Chris Carpenter won't undergo an MRI and evaluation in St. Louis until Thursday, but Cardinals manager Tony La Russa already knows his situation is neither good nor short-term.

"He's got a rib-cage injury," La Russa said plainly of the injury the St. Louis ace suffered while batting in the third inning of Tuesday night's game. "If it's not bad, four weeks. Bad, it's eight weeks."

Either way, the Cardinals will trudge on at least a month without their ace and mood-setter, whose tidy pitching after a two-year absence has highlighted the team's fast start.

St. Louis placed Carpenter on the 15-day disabled list prior to Wednesday afternoon's game here against the Diamondbacks. Also optioning right-hander Brad Thompson to Triple-A Memphis, the Cardinals added righties Mitchell Boggs and Chris Perez to fill the two staff spots.

But neither is going to fill the role and influence Carpenter has on this team.

Asked whether the effect of Carpenter's injury extends beyond the loss of a pitcher, La Russa said, "Yes."

"We don't talk about it a lot," he went on, "because pretty soon some guys might start thinking, 'Oh, we can't win without him.' The players respect what he means to us -- which is a lot.

"He's great. At least it's not his arm; guess the glass is half-full, rather than half-empty."

Carpenter had been disabled eight times since 1999 with shoulder and elbow injuries.

As for his pessimism regarding the duration of Carpenter's absence, La Russa simply said, "Players get that injury all the time," implying the track record for recoveries.

The ill-timed injury knocked Carpenter off a typical peak. Not only hasn't he allowed an earned run in 10 regular-season innings, but he had authored an encouraging Spring Training during which he fashioned an ERA of 1.52 across 23 2/3 innings.

Tom Singer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.