As the Cubs prepared for Saturday night's game against the Cardinals, manager David Ross provided a laundry list of updates on four players on the injured list.
Sunday, swingman Alec Mills will make a rehab start and reliever Trevor Megill will throw live BP with Triple-A Iowa.
Mills landed on the IL last Sunday with a lower back strain, and Megill has been sidelined since April 30 with a right forearm strain.
Mills holds a 5.96 ERA in 12 appearances this season but has been a Swiss army knife out of the bullpen, pitching in a variety of roles.
Megill impressed before being sidelined, throwing two scoreless innings against Atlanta last month. The right-hander is one of few pitchers on the entire Cubs' staff whose fastball velocity sits in the upper 90s.
Two more Cubs relievers have gone down in recent days. The club placed Justin Steele (right hamstring strain) on the IL Friday, and right-hander Jason Adam underwent surgery that night after dislocating his left ankle with Iowa.
Jake Marisnick, Jason Heyward hamstring updates
Ross acknowledged fourth outfielder Jake Marisnick will "at some point" need a rehab assignment in his return from a right hamstring strain.
Marisnick took dry swings Friday and is "on a good progression" as he works his way back, Ross said. The 30-year-old landed on the IL May 11, sustaining the injury two days prior while chasing after a fly ball against the Pirates.
Marisnick has provided a spark to the Cubs' lineup this season, batting .264/.350/.623 in 27 games while earning more playing time for his performance.
Jason Heyward, on the IL since Thursday with a left hamstring strain, did light agility work Saturday that went well, per Ross.
"J-Hey, depending on if this thing continues to bounce back pretty fast, we may just activate him when he's ready," Ross added.
Heyward is batting .183/.254/.341 in 39 games.