BOSTON (CBS) –  The Boston Red Sox have promoted pitcher Aaron Cook to the Major League roster, who will start Saturday against the Baltimore Orioles.

Cook will take Josh Beckett’s turn in the Boston rotation, who is getting some extra rest with a sore right lat muscle. Beckett threw 126 pitches in his last outing, a 4-1 loss to the White Sox, but Valentine said earlier this week he is optimistic the Sox right-hander will be able to make his next start.

To make room for Cook on the 25-man roster, the Red Sox optioned Jose Iglesias to Pawtucket. Iglesias went 2-for-3 in Pawtucket’s 6-4 loss Thursday night.

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To create a spot on the 40-man roster, Carl Crawford has been transferred to the 60-day disabled list.

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Crawford began the season on the 15-day DL as he rehabbed from off-season surgery on his left wrist, and is also currently dealing with sprained ligament in his left elbow.