The 21-year-old debuted in Friday's 16-2 win over the A's, entering as a defensive substitution in the seventh inning. He was 0-for-1 with a walk and a run scored.
Moncada hit .294 with 15 home runs and a .918 OPS while splitting time between Class A Advanced Salem and Double-A Portland prior to his callup before this series.
Manager John Farrell said Friday that Moncada will primarily play third base against right-handers, and he can bring speed and defensive versatility off the bench. Righty Daniel Mengden is on the hill Saturday for Oakland.