CHICAGO -- The Cubs are hoping not to be without Jon Lester for too long, but the team is starting to make plans for his absence in the rotation.

During an off-day on Tuesday, manager Joe Maddon said in an interview on 670 AM radio that Lester will miss at least one start and possibly two with a left hamstring injury that flared in Monday's 10-0 win over the Pirates. That means the Cubs will need to name a replacement starter for Sunday's game against the Angels and a trip to the injured list appears likely for Lester.

"Of course he's going to miss a start," Maddon said. "We'll start developing Plan B. We have different options."

Lester underwent an MRI exam on Tuesday, but the results of the tests were not immediately known. The Cubs are expected to provide more details on the severity of Lester's injury -- one stemming from running the bases in the second inning on Monday -- prior to Wednesday's game against the Pirates.

The top option would typically be left-hander Mike Montgomery, but he is on the 10-day injured list with a left lat injury and is not eligible for activation until Monday at the earliest. The next alternative would be right-hander Tyler Chatwood, who is in the bullpen and has not worked more than two innings in a game since March 6 during Spring Training.

The current healthy starting options from the Minor Leagues who are currently on the 40-man roster include Duane Underwood Jr. (Triple-A Iowa) and lefty Justin Steele (Double-A Tennessee).

"We have to figure out how we're going to work it from there," Maddon said in the radio interview. "[Montgomery] is on the DL right now, so you have to wait on him. I think Tyler Chatwood has been throwing the ball well. And again, I don't even know if the [front office] guys upstairs have other thoughts regarding this."

If Lester is placed on the injured list as anticipated, the Cubs would promote an extra relief pitcher for the next three games. That would give Chicago the option of getting Chatwood prepped for the Sunday start against the Angels or waiting to promote a starting pitcher from the Minors for that game.