Phillips was optioned to Triple-A Norfolk on Wednesday.
Phillips was sent back to the minors after allowing four runs on two hits and two walks during Wednesday's loss to the Mets. The 23-year-old now owns an unsightly 13.03 ERA, 2.07 WHIP and 6:10 K:BB through 9.2 innings this season. A corresponding roster move will be announced prior to Friday's series opener against the Indians.