Montero will undergo Tommy John surgery Tuesday, Matt Ehalt of The Bergen Record reports.
Tommy John surgery was the assumed outcome for Montero after he was diagnosed with a complete tear of his UCL on Thursday. He will miss the entire 2018 season and a typical recovery timeline would see him missing most of the first half of 2019 as well. It could be a tough road back for Montero, as he'll then be a 28-year-old with a 5.38 career ERA coming off a major injury.