Chicago White Sox pitcher Michael Kopech suffered a torn UCL in his pitching elbow, and will likely have to undergo Tommy John surgery, the team announced Friday.

Kopech, the top pitching prospect in the team’s system, made his MLB debut this season, but wouldn’t be able to pitch again until at least spring training in 2020 if a secondary diagnosis confirms the injury.

Kopech has a 1-1 record and a 5.02 ERA in four starts with the White Sox this season.

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