CHICAGO (CBS) — Cubs pitcher Yu Darvish has been sidelined for the rest of the season after an MRI showed a stress reaction in his pitching arm.

Darvish only pitched one inning in a rehab start in a Class A minor league game in South Bend on Sunday. He left the game after throwing warm-up pitches and appeared to aggravate the arm injury.

The Cubs signed Darvish to much fanfare to a  a six-year, $126-million deal.

Darvish had Tommy John surgery in 2014, then missed all of 2015. He made 17 starts in 2016 and 31 starts in 2017, when he was an All-Star.

Some concern surfaced across baseball regarding Darvish’s performance at the end of the season, as the Astros crushed him twice in the World Series, including the deciding Game 7.