The Red Sox activated Guerrero (shoulder) from the 15-day injured list Sunday, per Ian Browne of MLB.com.
Guerrero will return to the big-league club after being sidelined since Sept. 1. Through 38 games this season, the 35-year-old owns a 3.26 ERA, 1.14 WHIP and 36:7 K:BB over 38.2 innings. Boston optioned Wyatt Olds to Triple-A Worcester to make room for Guerrero on the active roster.