Peterson will return to the rotation to start Monday against the Phillies, Anthony DiComo of MLB.com reports.
Peterson moved to the bullpen earlier in the weekend, though the arrangement was evidently a very temporary one, as he'll return to the rotation after pitching just once in relief. Peterson has been a useful arm for the Mets in 29.2 innings this season, posting a 3.03 ERA, though his 17.4 percent strikeout rate and 10.7 percent walk rate indicate some regression could be coming.