CHICAGO -- Chicago Cubs ace Jon Lester is being placed on the 10-day injured list because of a hamstring injury suffered in Monday's home opener against the Pirates, a source said Tuesday.

Lester was scheduled to get an MRI on Tuesday, an off day for both teams, who meet again Wednesday.

Appearing on 670 The Score radio Tuesday, Cubs manager Joe Maddon said that Lester will miss one or two starts but didn't confirm a trip to the IL.

Lester left the game in the third inning Monday with left hamstring tightness, and the Cubs went on to a much-needed 10-0 victory.

Lester sent out a tweet about his injury earlier Tuesday. It was not clear if he knew at the time that he was heading to the IL.

Sometimes when you have elite speed these things can happen. Great to get the W in front of the home crowd though, here's to many, many, many more! #NVRQT

— Jon Lester (@JLester34) April 9, 2019

"I didn't feel anything as far as a pop or anything like that," Lester said after the game. "Kind of more along the cramping sensation. We'll find out more [Tuesday]."

Lester's injury occurred while he was running the bases in the bottom of the second inning. He slid into second base on an RBI double and moments later slid into home as part of a six-run inning by the Cubs. The veteran says he's never had leg problems before. (Lester, 35, has made at least 31 starts every season since 2008.)

"In my mind, I'm making my next start," he said. "[Tuesday] may tell us something different."

While warming up before the top of the third, Lester grabbed his left hamstring. He then faced two batters, allowing both to reach, before Maddon went and got him. Brad Brach replaced Lester.