Dr. James Andrews performed the operation in Pensacola, Florida. The procedure wasn't a surprise, as it came after Dunning began experiencing forearm discomfort in his throwing arm in late February and after a 2018 season in which he was shut early because of an elbow sprain.
Dunning, 24, is ranked as the No. 80 prospect in baseball by MLB Pipeline and the No. 6 prospect in the White Sox's system. He had a 2.71 ERA and 1.19 WHIP in 86 1/3 innings split between advanced Class-A and Double-A in 2018.
The recovery timeframe for Tommy John is at least a year and usually more, meaning Dunning will be out all of 2019 and likely will have the start of his 2020 season delayed.