Richard is on the 15-day disabled list with a blister on his left middle finger and has gone 0-1 with one save and a 7.30 ERA (10 ER/12.1 IP) in 22 relief outings for the Cubs this year.

La Stella, 27, is batting .291 (23-for-79) with eight doubles, two home runs and seven RBI in 38 games for the Cubs this season.

"They're both ready to roll," Cubs manager Joe Maddon said Sunday to reporters.