Phelps was diagnosed with a torn UCL and will undergo Tommy John surgery, Ryan Divish of The Seattle Times reports.

EDGE Analysis

This is a tough blow for the Mariners and Phelps, as the veteran reliever was expected to play a key role in the team's bullpen this season. The 31-year-old apparently suffered the injury during his outing against the Angels last week. Given Tommy John surgeries typically carry a 12-to-18 month recovery timeline, Phelps will likely open the 2019 season on the disabled list. This comes after he missed the final month of the 2017 season after undergoing elbow surgery to remove a bone spur. With Phelps unavailable, Juan Nicasio, Nick Vincent and James Pazos will likely be tasked with getting the ball to Edwin Diaz.