Kopech's peripherals are straight up concerning. Tyler Wells, who also was a reliever last year and transitioned into a starter this year, is having a much better time with the change than Kopech. And Kopech was a much better prospect than Wells.
His slider had problems last year too, especially in the 2nd half. Remember when Cleveland basically didn't swing at his slider in that game they got 7 runs off Kopech last year?