Chicago Cubs starting pitcher Yu Darvish was forced to leave his Class A assignment after just one inning and has asked for an MRI, according to Steve Greenberg of the Chicago-Sun Times.

Darvish signed a a massive six-year, $126 million deal with the Cubs in the offseason, but he went to the disabled list in late May due to a right triceps injury. It took three months for Darvish to get back into baseball, but now it's anybody's guess how long he'll be out for following a potential setback.

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In eight starts with the Cubs prior to his injury, Darvish went 8-8 with a woeful 4.95 ERA and 49 strikeouts in 40 innings pitched. Given his strong track record, however, it was easy to believe that Darvish was on the verge of bouncing back. Now, there's plenty of doubt if he'll even return in 2018.

The Cubs have a four-game lead on the St. Louis Cardinals for the NL Central lead, and their rotation has performed just fine. But Darvish was paid big money to front a rotation that lost Jake Arrieta to the Philadelphia Phillies in free agency, so this has obviously been a massively disappointing year for him.

Veteran standout Jon Lester continues to lead the Cubs rotation (13 wins, 3.72 ERA), while Jose Quintana and Kyle Hendricks are holding the fort down. But as the Cubs try to push for a second championship in three years, they need a veteran ace like Darvish in October. If the Cubs don't think he's coming back in 2018, perhaps Theo Epstein will add another veteran arm via trade.

It's been a frustrating season for many of baseball's top pitchers, with Noah Syndergaard, Aaron Sanchez and now Darvish having lost seasons with hand/arm-related injuries. It's become an unfortunate trend in baseball throughout the years, and there's no quick fix for teams to ensure the long-term health of their top pitchers.

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