BOSTON -- First baseman Glenn Davis, who had been expected to return to the starting lineup in the next few days, has been placed on the 15-day disabled list by the Orioles.

The move is retroactive to April 7, the day after the season started, meaning Davis will be eligible to return April 22, a week from tomorrow. The decision was made this morning, and outfielder Luis Mercedes has been recalled from Rochester to take Davis' spot on the roster.

Davis, suffering a strain of the rib cage muscle, has missed six games after playing in the 2-0 victory over Cleveland on Opening Day. "Originally it was thought he'd be out only a day or two," said manager John Oates, who met with general manager Roland Hemond and assistant GM Frank Robinson last night.

"But after talking to Glenn and the doctors, our feeling is that he'll need a couple of days to swing the bat before coming back," said Oates. "So, why go another week playing a player short?"

The recall of Mercedes will give Oates some flexibility he hasn't had for the last week. "Luis will play leftfield and bat second here Thursday [when lefthander Joe Hesketh will face the Orioles]," said Oates.

"Then we'll get [lefthander] Scott Aldred in one game at home, where he'll play rightfield. Beyond that, we'll wait and see. He gives me a righthanded hitter on the bench who can run."

The Orioles originally thought Davis would return to the lineup during the current series against the Red Sox, which continues here tomorrow and concludes Thursday night. But the first baseman, who missed most of last year with a neck injury, suffered a setback when he had another spasm while doing his exercises over the weekend.