Frankie Montas scratched from start Friday

Photo by Thearon W. Henderson/Getty ImagesOakland A’s ace Frankie Montas was scratched from his start Friday against the San Francisco Giants due to upper back tightness, per a team announcement.

The right-hander is among the best pitchers in the league so far, earning AL Player of the Week honors last week. Overall for the season his numbers look like this through four games, three of which were A’s victories:

Montas: 1.57 ERA, 23 ip, 22 Ks, 9 BB, 0 HR, 14 hits, 2.47 FIP

For now, Montas’ status is day-to-day. There is still hope he could return to pitch in this weekend series against the Giants, reports Susan Slusser of the S.F. Chronicle.

In his stead, rookie left-hander Jesús Luzardo will…