Mastrobuoni is out of the lineup for Sunday's game against the Diamondbacks.
Mastrobuoni started at third base in each of the Cubs' final five games before the All-Star break as well as Friday's 5-2 loss to Arizona, but he'll hit the bench for the second day in a row to close out the series with the Diamondbacks. The 28-year-old no longer looks slated to get regular playing time moving forward after the Cubs brought Mike Tauchman back from the injured list Friday.