Right-hander Zach Stewart, whom the White Sox traded along with Brent Lillibridge for Kevin Youkilis last June, was claimed off waivers from the Pittsburgh Pirates.
Stewart, 26,was 1-4 with an 8.58 ERA in 20 games last season between the Sox and Boston.
In 11 starts for AAA Pawtucket in 2012, Stewart was 3-5 with a 3.94 ERA. The Red Sox traded him to the Pirates on Nov. 28 for pitcher Kyle Kaminska. The Pirates then designated him for assignment on January 17.
The Sox 40-man roster stands at 39 and is expected to reach 40 with the announcement of free right-hander Matt Lindstrom's signing.