Naughton underwent an MRI on Saturday that revealed a Grade 1 UCL strain, Jeff Fletcher of The Orange County Register reports.
Naughton was traded from the Reds to the Angels last August and was expected to begin the 2021 season at the Triple-A level. However, he'll now be sidelined due to his left elbow injury. It's not yet clear when the 24-year-old will be cleared to return to action.