To make room on the roster, the club demoted right-hander Matt Barnes to Pawtucket.
The 25-year old Shaw is with the club for the second time this season. His stay is expected to be short because Boston is dealing with a potential shortage with its corner infielders.
Third baseman Pablo Sandoval left Saturday's game with tightness in his right quadriceps. He started Sunday.
First baseman Mike Napoli has struggled at the plate, hitting .200 with nine homers and 26 RBIs. He was rested Saturday and is not in the lineup Sunday.
The 24-year old Barnes (2-2) took the loss in Saturday's game.