Grilli hasn't pitched since straining his left oblique in late April. Manager Clint Hurdle says the right-hander will make a couple of appearances in middle relief before the team determines whether to return Grilli to the back end of the bullpen. The 37-year-old is 0-1 with four saves in seven opportunities this year.
Mark Melancon has seven saves in eight chances filling in for Grilli.
Sanchez hit .278 with two homers and 12 RBIs in 21 games for Pittsburgh but was forced back to the minors when the team activated Russell Martin off the disabled list Thursday.