Following Saturday's 5-1 win over the Orioles, the team had not announced a starter. Jeremy Hellickson had been scheduled to make his 31st start of the season but threw 41 pitches in relief during Friday's 18-inning contest, the longest game in franchise history.
De Los Santos, who has never appeared in a Major League game, compiled a 5.34 ERA over 26 appearances for Triple-A Durham this season.
Sam Strong is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.