The Red Sox activated Seigler (knee) from the 10-day injured list Friday and optioned him to Triple-A Worcester.
Seigler began a rehab assignment with Worcester on Thursday after recovering from left knee patellar tendinopathy, and the Red Sox will keep him with their top minor-league affiliate rather than add him to the active big-league roster. The 26-year-old utility player was acquired via trade from the Brewers over the offseason.