Manager Buck Showalter said that Walker (shoulder) will need to make at least one rehab start before returning from the 10-day injured list, Mike Puma of the New York Post reports.
Walker left his start Monday against the Phillies after just two innings due to shoulder bursitis. Given that he'll require a rehab outing, Walker seems likely to miss more than one turn in the major-league rotation. David Peterson is likely to take his place temporarily, though the Mets have yet to officially announce their plans.