Santos was recalled by the Giants on Thursday, Maria I. Guardado of MLB.com reports.
Santos hasn't experienced much success with Triple-A Sacramento to begin the season, maintaining a 4.50 ERA with a 1.67 WHIP and 10:6 K:BB across 12 innings. He'll provide depth in the bullpen for the big-league club during a bullpen game Thursday, though his stint with the big-league club could be short-lived.