Lackey, 38, is 5-9 with a 5.20 ERA in 17 starts this season. He's tried to pitch despite the soreness in his foot, and was examined on Thursday by the Cubs' medical staff.
"If everything goes according to what we believe, he should be able to go post-break," manager Joe Maddon said.
• Kyle Hendricks, on the disabled list since June 5 with inflammation in his right hand, is expected to throw his second bullpen session on Saturday. That will only be the second time he's thrown off the mound since he went on the DL. Hendricks said he may need one more bullpen session after Saturday and could then be ready for a rehab assignment.
• With the Cubs' decision to go with young catchers Willson Contreras and Victor Caratini, could they be looking for a veteran catcher by the non-waiver Trade Deadline? Not necessarily, president of baseball operations Theo Epstein said.
"[Caratini] carries himself more like a veteran than a typical rookie catcher," Epstein said.
• Cubs pitcher Jon Lester and his wife Farrah raised more than $600,000 at their NVQT fundraiser on Wednesday night. The money will go toward pediatric cancer research.