Dunning (elbow) underwent Tommy John surgery Monday, Daryl Van Schouwen of the Chicago Sun-Times reports.
Dunning was shut down with forearm discomfort earlier in camp, though it was decided surgery was necessary Monday. Coming off a sprained elbow to close 2018, Dunning will now face a long rehab process and miss the entire 2019 season and likely the beginning of the 2020 season as well.