He hasn't pitched since July 22 after being injured with a strained right forearm. Mark Melancon has converted eight saves in nine opportunities in Grilli's absence.
Grilli has converted 30 of 31 save opportunities and is 0-1 with a 2.34 ERA, 0.92 WHIP and 66 strikeouts in 42.1 innings this season. He was leading the National League in saves when he was injured.
"We'll use him at least a couple times in non-leverage situations to see how he fares, how he feels," Pirates manager Clint Hurdle said Tuesday.
The Pirates (80-57) are three victories away from securing their first winning season since 1992.