The oft-injured Sizemore was signed by the Red Sox in the offseason to a one- year contract worth $750,000 and eventually won the starting center fielder job over Jackie Bradley Jr. after an impressive spring training.
Sizemore's level of play did not continue during the regular season. The 31- year-old batted .216 with two home runs and 15 RBI in 52 games.
This season was his first in the majors since 2011 due to knee and back injuries. He has also undergone seven surgeries since the '09 season.
The three-time All Star was a standout outfielder during his time with the Cleveland Indians. He hit .290 while leading the majors in runs (134), doubles (53) and extra-base hits (92) in 2006. With 11 triples and 28 home runs that season, Sizemore became just the fourth player with a 50-double, 10-triple, 25-homer season.
A lifetime .266 hitter, Sizemore has compiled 226 doubles, 45 triples, 141 homers, 473 RBI, 139 stolen bases and 615 runs scored in 944 games and won back-to-back gold gloves in 2007 and 2008.
Boston also recalled third baseman Garin Cecchini from Triple-A Pawtucket to fill Sizemore's roster spot.
Cecchini returns to the lineup for the second time this season. In 62 games with Pawtucket this season, he has batted .263 with a club-leading 56 hits and 24 RBI.