The Phillies optioned De Los Santos to Triple-A Lehigh Valley on Tuesday, Matt Gelb of The Athletic reports.
The move opens up a spot on the active roster for Nick Pivetta, who will be officially recalled from the minors ahead of his scheduled start Tuesday against the Cardinals. The Phillies still view De Los Santos as a starter over the long haul, so he'll get the opportunity to slot into the Lehigh Valley rotation after seeing limited action of late out of the big-league bullpen. Since being summoned back to the majors May 17, De Los Santos made a pair of two-inning relief appearances, conceding three runs on two hits (both home runs) and a pair of walks.