Mejia is scheduled to start Saturday's game against the Phillies.
He'll be awarded a second straight turn through the rotation after he limited the Pirates to two runs while striking out seven over five innings in his Arizona debut Monday. The 24-year-old right-hander might not have much longevity in the rotation with Arizona expected to get Luke Weaver (shoulder) back from the 60-day injured list and Merrill Kelly (illness) back from the COVID-19-related injured list within the next couple of weeks.