The Phillies had designated Sizemore for assignment last Friday.
The 32-year-old is hitting .245 with six RBIs in 39 games this season. He signed a minor league deal with Philadelphia in June of 2014 after being released by the Boston Red Sox.
Sizemore was named an All-Star in three straight seasons from 2006-08. His best year came in 2006, when he hit .290 with 28 home runs, 53 doubles and 76 RBIs.
In 2010, Sizemore underwent microfracture surgery on his left knee. He returned in 2011 but was limited due to back and knee injuries and underwent microfracture surgery on his right knee in 2012. He did not play in either of the 2012 or 2013 seasons.
The Phillies (19–33) host the Cincinnati Reds on Tuesday.
- Molly Geary