The Reds optioned Phillips to Triple-A Louisville on Wednesday, Gordon Wittenmyer of The Cincinnati Enquirer reports.
Phillips has a 5:3 K:BB over six scoreless innings this spring but nonetheless finds himself sent to minor-league camp. The talented 22-year-old could still wind up making a decent number of starts for the Reds this season, but there are currently others ahead of him in the pecking order.