The Chicago Cubs have had some serious issues with their pitching staff this season, and they’re once again playing the waiting game with hurler Yu Darvish.

Darvish, who was placed on the disabled list over the weekend with tendonitis in his right triceps, will undergo an MRI on Tuesday to check out the extent of the damage to his arm, according to multiple reports.

It’s unclear just how bad that damage may be, but Darvish has a bit of a history with arm trouble. He was sidelined late in 2014 and for the entire 2015 season after elbow discomfort resulted in Tommy John surgery, and he is in his second stint on the disabled list this season after dealing with a mysterious flu bug earlier in the year.

Whatever the results of Tuesday’s MRI are, Darvish’s health has to be a concern for the Cubs, as they’ve gotten inconsistent production out of the back part of their rotation this season. Tyler Chatwood has been unable to find his groove with serious control issues, and even stalwarts like Jon Lester and Jose Quintana have had trouble getting deep into games, resulting in an over-taxed bullpen early in the campaign.

If Darvish is out for an extended period, then the Cubs could either convert Mike Montgomery into a full-time starter, which would be a palatable option after his dominant performance against the Pirates Monday, or they could call up a prospect like Adbert Alzolay or Duane Underwood, who has a 3.35 ERA in eight starts with the Triple-A Iowa Cubs this season.