SEATTLE — Salvador Perez came through once again for the Royals, and on Thursday, it was in a grand way.

Perez’s grand slam rocketed the Royals to a 6-4 series-opening win over the Mariners at T-Mobile Park, snapping Kansas City’s two-game losing streak and giving the club its eighth win in the past 11 games.

One day after Whit Merrifield’s grand slam in Houston, Perez launched a 2-0 sinker from Mariners reliever Joe Smith in the top of the sixth inning a projected 418 feet into the left-field stands. It was his 35th homer of the year and 13th go-ahead blast this season.

It was the first time in franchise history that the Royals hit grand slams in back-to-back games.

And it swung all the momentum back into the Royals’ dugout. An inning before, starter Brad Keller had exited with an injury after he allowed a home run to Kyle Seager in the bottom of the fifth. Keller, who allowed two runs and threw 79 pitches in 4 1/3 innings, grabbed his arm after throwing a sinker down the middle and exited the game with an injury later described as posterior right shoulder discomfort.