The 27-year-old Peña has posted no record with four saves and a 1.86 ERA (2 ER/9.2 IP) in eight relief appearances with Iowa this season. He has struck out 11 batters in 9.2 innings while limiting opponents to a .212 batting average. He made his big league debut with the Cubs last season, posting no record with a 4.00 ERA (4 ER/9.0 IP) in 11 relief outings. He struck out 13 batters in the nine innings pitched.
The 6-foot-2, 185-pound Peña originally signed with the Cubs as a non-drafted free agent on March 9, 2009 out of San Pedro de Macoris, Dominican Republic. He is 29-39 with 11 saves and a 3.76 ERA (267 ER/638.1 IP) in 187 minor league appearances (78 starts) covering nine minor league seasons.
Grimm, 28, is 1-0 with a 7.30 ERA (10 ER/12.1 IP) in 12 relief outings with the Cubs this season.