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06/29/09 9:40 PM ET

Rasmus diagnosed with hernia

Cards rookie finally has answer to nagging pain

ST. LOUIS -- Cardinals outfielder Colby Rasmus has been diagnosed with a hiatal hernia and was unavailable for Monday night's series opener against the San Francisco Giants.

Rasmus, who is in the midst of a 2-for-24 slump, has been dealing with pain in his stomach for some time.

"It's been going on for a while, but I've been dealing with it," Rasmus said. "Finally, I just wanted to get it checked out and see what was going on."

Rasmus was told not to play on Monday night because he was put to sleep for the examination and was still feeling some drowsiness. He started Saturday's game and made a pinch-hit appearance on Sunday before deciding to opt for help.

It was prescribed that Rasmus not eat late at night, something tough for a Major League player to avoid.

"I was eating a lot late at night, and it was sitting on my stomach," Rasmus said. "I have to switch that up to more in the morning and less at night.

"I just have to change the way I eat. Usually when I wake up, it's the worst. It's not that big of a deal, just [wanted to] get it figured out and get it fixed."

The rookie said he would be available for Tuesday night's game against the Giants, but with left-hander Randy Johnson on the mound, he may not be in the lineup.

Rasmus is hitting .262 with seven home runs and 28 RBIs.

B.J. Rains is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.