SEATTLE -- Salvador Perez knew that he hadn’t had much success off of Mariners reliever Joe Smith in the past, with three strikeouts in six at-bats entering the sixth inning on Thursday night. But with the bases loaded and nobody out, Perez knew he had to come through.

He also knew what kind of pitcher Smith is, with a signature sinker that he likes to throw inside to right-handers.

So when Perez took two of Smith’s sinkers inside for balls, the Royals catcher had a suspicion that another one was coming in the zone. And when Smith left it a little too much over the plate, one swift and powerful swing from Perez turned a three-run deficit into a one-run lead in the Royals’ eventual 6-4 series-opening win over Seattle at T-Mobile Park.

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“I was trying to do my job,” Perez said. “I was trying to bring my guys home. And I hit the ball super hard.”

The win snapped Kansas City’s two-game losing streak and gave the club its eighth win in the past 11 games.

One day after Whit Merrifield’s grand slam in Houston, Perez’s offering traveled a projected 418 feet into the left-field stands. It was the first time in franchise history that the Royals hit grand slams in back-to-back games.

“What’s so impressive is that it doesn’t surprise you when he does it,” manager Mike Matheny said. “That’s such a great compliment. This guy has been so consistent in those situations.”

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.

Reliever Joel Payamps took over, and the Mariners quickly took a 4-0 lead on Jake Fraley’s two-run homer. That would be all the offense the M’s would get off the Royals’ weary bullpen -- a unit that’s missing some of its bigger names, but one that received crucial innings from Richard Lovelady, Ervin Santana (1-1) and Scott Barlow, who notched his ninth save a day after throwing 31 pitches in 1 1/3 innings.

“It was just a really impressive job by a couple of guys who haven’t necessarily been in those spots,” Matheny said.

They were helped by the Royals' defense, which made elite plays all night. Center fielder Michael A. Taylor teamed up with shortstop Nicky Lopez and Perez for a jaw-dropping relay that got Mitch Haniger out at home in the first inning, limiting Seattle to just one run off Keller.

Andrew Benintendi robbed Jarred Kelenic of a home run in the eighth inning with a perfectly timed jump at the left-field wall, causing Kelenic to put his hands to his head in disbelief and Santana to point to Benintendi in gratitude.

“One right after the other, you just don’t see games like that,” Matheny said. “That keeps you in the game for some incredible offense.”

The Royals had managed just one hit against Mariners starter Yusei Kikuchi as they entered the sixth inning. The lefty was working at a fast tempo and had struck out three, needing just 56 pitches through five innings.

But Ryan O’Hearn and Emmanuel Rivera hit back-to-back singles to lead off the inning, and the Royals got on the board with Whit Merrifield’s RBI double to start the rally.

When Nicky Lopez walked to load the bases, Perez did what he’s been doing all season: Powered the Royals to a win. The slam was his 35th homer of the year and 13th go-ahead blast this season.

Perez admitted with a grin that when he came up to bat with the bases loaded again in the ninth, he might have been thinking too much about another grand slam.

After all, only 13 players have ever had two grand slams in a game, including Fernando Tatis’ two in one inning feat in 1999.

“I almost ended up in the club,” Perez said.

Alas, Perez grounded out to end the inning. But who knows what Friday will bring?

“I’m not surprised,” Santana said. “Because I know how talented he is. He trusts his ability. He doesn’t try to put any pressure on himself. And in those big situations, he’s very relaxed and waiting for his pitch.”