Red Sox starting pitcher Michael Wacha delivers a pitch in the first inning against the Orioles on Saturday in Baltimore. Terrance Williams/Associated Press

BALTIMORE — Kiké Hernández hit a two-run homer, Christian Arroyo added a key RBI double in the ninth inning and Michael Wacha pitched scoreless ball into the sixth as the Boston Red Sox beat the Baltimore Orioles 4-3 on Saturday.

The teams split the first two games of the series and the finale will be played in Williamsport, Pennsylvania, on Sunday

The Orioles slipped to 2 1/2 games behind Tampa Bay in the race for the third and final American League wild-card spot.

One day after scoring a season-high 15 runs, Baltimore was held scoreless until the seventh when rookie Kyle Stowers drove in a run on a fielder’s choice and Jorge Mateo scored on a wild pitch by John Schreiber that cut the lead to 3—2.

Boston added an important insurance run in the ninth Arroyo’s RBI double, completing a 3-for-5 day.

Garrett Whitlock allowed a run on a fielder’s choice but got the final six outs for his fifth save of the season.

Wacha (8-1) made his second start since being reinstated from the IL on Aug. 14. He allowed four hits with four strikeouts and one walk over 5 2/3 innings, lowering his ERA to 2.28.

The Red Sox took a 1-0 lead in the fifth on a run-scoring single by Alex Verdugo off Kyle Bradish, who had managed to strand runners on first and third to minimize the damage.

Hernández hit a two-run shot that stayed just inside the foul pole in left field in the sixth inning that extended the lead to 3-0. Hernández has five RBI in three games since returning from the IL. His last homer came against the Orioles on May 29.

Bradish (1-5) allowed three runs and nine hits with six strikeouts over 5 2/3 innings.

TRAINER’S ROOM

Red Sox: Tommy Pham was held out of the lineup after leaving Friday’s game with low back tightness. “He might push to play tomorrow. We’ll see how he feels,” Boston Manager Alex Cora said. … 1B Eric Hosmer left Saturday’s game with the same issue.

Orioles: OF Cedric Mullins was held out of the lineup with a sore shin after fouling a ball off his leg a night earlier.