Kopech struck out 15 batters in four Major League starts this season.
White Sox starter Michael Kopech will likely need to undergo Tommy John surgery, the team announced on Friday. He is expected to miss the entire 2019 season.
The White Sox also said that Kopech will receive a second opinion in the coming days to confirm the diagnosis.
Kopech, Chicago's top-ranked pitching prospect, made four starts in 2018, striking out 15 batters in 14 1/3 innings. He allowed just one earned run in his first three starts before giving up seven runs in 3 1/3 innings on Sept. 5.
Kopech was drafted by Boston with the 33rd pick of the 2014 MLB Amateur Draft. The Mount Pleasant, Texas native currently ranks No. 13 on Baseball America's Top 100 prospects list.
The White Sox currently sit in 4th place in the AL Central at 56–84. They are 24 games behind the division-leading Indians.