The move will push right-hander Kyle Hendricks back a day, as he'll start Saturday, and Jake Arrieta is scheduled to pitch Sunday's series finale on normal rest.
"It's not bad to give Kyle an extra day. That still keeps Jake on his normal day," Cubs manager Joe Maddon said. "You don't want to really backlog Jon that much. ... It worked out really well.
"Jon fits easily into that Friday, then you give Kyle the extra day, which we like. It just played really well."
Lester threw only 31 pitches against the Pirates on Monday night, when the game was postponed after four innings due to inclement weather.