Peterson is slated to pitch Wednesday versus the Nationals, either as a traditional starting pitcher or bulk reliever, Anthony DiComo of MLB.com reports.
Peterson has posted a 6.41 ERA in four starts this season, but he pitched better his last two times out. While working behind an opener this past Sunday against the Cubs and then pitching in long relief in Thursday's win over the Twins, Peterson covered seven innings and gave up one earned run on seven hits and one walk. The left-hander will likely be on a short leash Wednesday, but Peterson will be afforded another opportunity to restate his case for a rotation spot.