Mastrobuoni went 0-for-2 with two walks, a stolen base and a run scored in Sunday's 11-5 loss to the Red Sox.
Mastrobuoni has been in the lineup in two of three games since the All-Star break, but he's gone hitless over six at-bats. He's faced right-handed pitchers both times, suggesting he could be carving out a platoon role at third base that could eat into Patrick Wisdom's playing time. Mastrobuoni will need to do a bit more with the bat to maintain his newfound role -- he's slashing just .155/.268/.197 with seven steals, one RBI, seven runs scored and three doubles over 84 plate appearances this season.