Lagares has been on the disabled list since June 16 with a sprained left thumb. He's finishing up a rehab assignment in Double-A Binghamton, where Jose Reyes is also playing while preparing for his return to the Mets.
Granderson, who is dealing with a right calf strain, said he isn't sure when he'll return but he likely won't need time on the disabled list. He planned to throw and hit before Friday's game but has not resumed running.
"The big concern is running and being in the situation where I have to try to beat out a single or score from first or from second," Granderson said. "And we turn something that is slight to possibly a day or two to potentially something that could be six to eight weeks. It's risk-reward."
Granderson said he injured the smaller of the two muscles in the right calf, which lends itself to fewer health problems.
"The big thing is just rest right now and trying to stay off it as much as possible," he said.
With Granderson out of the lineup Thursday, Collins inserted Brandon Nimmo into the leadoff spot. The rookie provided a spark, scoring the winning run in the Mets' 4-3 win, which snapped the team's four-game losing streak.
Lagares will provide depth to a team battling injuries. The center fielder, who was hitting .306 against lefties before his setback, will face Cubs left-hander Jon Lester in his return.
Joshua Needelman is a reporter for MLB.com based in New York. This story was not subject to the approval of Major League Baseball or its clubs.