De Los Santos carries a 3-0 record, 1.07 ERA, 1.34 WHIP and 33:11 K:BB across 25.1 innings through his five starts at Triple-A Lehigh Valley this season.
The 22-year-old's 11.8 K/9 is his highest mark at any level during his four seasons in the professional ranks, with his above-average fastball and improved slider in particular making life difficult for opposing hitters. According to Todd Zolecki of MLB.com, De Los Santos' early season performance has put him on the radar for a potential promotion to the Phillies at some point in 2018, though the righty's status as a non-roster player makes his ascent to the big leagues a little more difficult. Even so, if De Los Santos is able to trim down his walk rate while continuing to whiff batters at a prolific rate in his subsequent outings with Lehigh Valley, it may be difficult for the Phillies to justify keeping him on the farm much longer, especially if back-end rotation members like Vince Velasquez and Zach Eflin aren't able to consistently provide quality innings.