According to Jesse Rogers, who covers the Chicago Cubs for ESPN, a source has told him that Jon Lester is headed to the injured list.

Lester exited Monday’s game with left hamstring tightness. The injury appeared to happen while he was on the base path in the second inning after knocking in an RBI and later sliding into home plate. It’s still not clear when the injury occurred but it may have happened when he slid into home plate and appeared to be wincing on his way back to the dugout. He was later pulled in the third inning after initially saying he was fine to keep going.

Rogers broke the news live on Kap and Company on ESPN 1000

Joe Maddon said on 670 The Score this afternoon that Lester will miss Sunday’s start and maybe another.