Santana was optioned to the alternate training site Saturday, Ken Gurnick of MLB.com reports.
The 24-year-old has been in the majors all season, but he'll head to the alternate site with Pedro Baez (groin) returning from the injured list. Santana has a 5.29 ERA, 1.29 WHIP and 18:7 K:BB over 17 innings this season.