Pearson (elbow) underwent an MRI on Thursday, Kaitlyn McGrath of The Athletic reports.
The hard-throwing prospect was shut down earlier this week with elbow tightness, which is never a good sign. General manager Ross Atkins said the team is "not overly concerned," but that's pretty typical front-office speak with pitching injuries like this where there has not been an official diagnosis. Trent Thornton (elbow) is coming off the injured list to take Pearson's spot in the rotation.