The 27-year-old Grimm has no record and a 4.72 ERA (18 ER/34.1 IP) in 45 relief appearances with the Cubs this season. He has 38 strikeouts in 34.1 innings pitched, an average of 10.0 strikeouts per nine innings, while limiting opponents to a .235 batting average, including a .200 mark by right-handed hitters. Grimm had spent the entire season with the Cubs prior to being optioned to Triple-A following the game Saturday. He made one relief appearance for Iowa on Monday in Omaha, striking out three batters in a scoreless ninth inning.
Hammel, 33, is 11-5 with a 3.07 ERA (41 ER/120.1 IP) in 21 starts with the Cubs this season.