Hurdle announced Friday that Mark Melancon would close games for the Pirates in place of Grilli, who has blown four save opportunities this year after converting 33 of 35 chances last season.
''There's no safety net for a closer. There never is,'' Hurdle said before Pittsburgh's 6-3 loss to the Chicago Cubs. ''So he won't have to deal with that for a while, which I think will help.''
Grilli pitched a scoreless eighth inning in the series opener at Wrigley Field. He struck out the first two batters, then walked John Baker and gave up a single to Junior Lake. Luis Valbuena flied out to right to end the inning.
Grilli said he felt better after making a minor adjustment to his mechanics. He declined to elaborate when asked about the change.
''It's always good when the ball comes out the way it's supposed to,'' he said. ''It's one of those things where sometimes you get a little bit off kilter in the grind of the game. You get rid of what (the problem) was and fix it and get good results.''
Grilli allowed a tying homer to Devin Mesoraco in the ninth inning of Thursday's 4-3 victory over Cincinnati. The veteran right-hander, who made the All-Star team last year for the first time, yielded at least one run in three of his previous four outings, and his four homers allowed this season matches his total from all of last year.
The 37-year-old Grilli is 0-2 with 11 saves and a 4.12 ERA in 21 games this year. He was sidelined for a month after straining his left oblique in late April.
For now, Hurdle said he will use Grilli when the Pirates are trailing.
''He's all about doing what's best for the club and getting better,'' Hurdle said before the loss. ''We'll definitely need him as the season plays out.''
Melancon is 1-2 with 10 saves in 13 chances and a 1.89 ERA in 35 games this year. He has not allowed a run in eight games and 7 1-3 innings in June.
Hurdle said he also could use Tony Watson in a save opportunity.