The move comes as Sizemore struggles after injuries sidelined him between September 2011 and this season. He made the All-Star team three times with the Cleveland Indians then had seven operations since 2009, including surgery on both knees, his back and elbow.
Sizemore hit .333 in spring training and started in center field on opening day when he homered in Boston's 2-1 loss at Baltimore. But in 52 games, he hit .216 with two homers and 15 RBIs.
The Red Sox recalled third baseman Garin Cecchini From Triple-A Pawtucket. He played one game with Boston on June 1, going 1 for 2 with an RBI double in a 4-0 win over Tampa Bay.