SEATTLE -- Given how Freddy Galvis’ Reds tenure turned from a fast start to downward spiral, his $5.5 million club option for next season loomed large as his slump reached a 1-for-40 funk entering this week’s series against the Mariners.

But Galvis left T-Mobile Park as Thursday’s savior in the Reds’ 11-5 win, after he crushed a go-ahead grand slam during the seventh inning that saved Cincinnati from a sweep. Galvis pulled an 0-1 slider off reliever Dan Altavilla 385 feet into the right-field bleachers on a night that, to that point, the Reds bats had largely been sleepy in Seattle.

Acquired from the Blue Jays off waivers on Aug. 12, Galvis was essentially brought in to give Cincinnati leverage in its infield in 2020 and beyond, particularly after shortstop José Iglesias’ breakout season. Iglesias is earning $2.5 million on a one-year deal and almost certainly will command more dollars and years on the free-agent market this offseason.

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Enter Galvis, who offers versatility and longevity at a moderate price (he also has a $1 million buyout for ’20). But after a steep slump, when he went hitless in 12 of 13 games before this series, even Galvis had concerns about his future.

“I'm just trying to finish strong,” Galvis said. “I think, for me, it's really important, too. I've got one more option, and if not, I become a free agent. But I'm just trying to play baseball. Just trying to do my job and just trying to help the team win some games.

“Just being [in the Majors] for eight years, I just try to learn with a lot of stuff, going on outside of your head and just try to focus on what you have to do. Try to focus on doing your job, and that's what I'm doing right now.”

Galvis started at shortstop for the third time in 30 games. It’s the position he’s manned for 764 of his 884 big league starts. But the Reds acquired him to be their everyday second baseman -- at least for the remainder of ’19.

Iglesias’ plus-nine Defensive Runs Saved are tied for sixth-most among shortstops, and his .724 OPS is his highest since 2013, meaning his bat and defense are among the most valuable in the Reds’ lineup.

But Galvis originally played second when coming up with the Phillies in 2012 and ’13 and boasts the offensive potential to plug into the middle of the order, at least when he’s clicking. Galvis’ slam was his 23rd homer this season, surpassing his career high of 20, set in ’16. And Galvis showed his best during his first two weeks after being claimed, when he slashed .404/.420/.702 over his first 13 games with Cincinnati.

“When he first got here, he was swinging the bat well,” Reds manager David Bell said. “He's had a couple weeks where the results haven't been there, but with a guy like Freddy, I believe he can be a better player. He can keep getting better and better. But also, when you have a couple down weeks, we still know who we have. He's been a good player for a long time.”

Galvis also roped a 102 mph single in the eighth as part of a four-run inning, during which the Reds showed their most life of the series. Curt Casali and Eugenio Suárez each went deep with two-run shots that inning, with Suarez notching his 45th homer of the season to tie Mike Trout for second-most in the Majors, behind only the Mets’ Pete Alsono, who has 47.

Five of the club’s first seven batters walked against Mariners righty Justin Dunn in his Major League debut, but the Reds were only able to plate two in that frame. By the third, they trailed, 4-2, thanks in part to Seattle reliever Tommy Milone retiring each of his first 11. Milone was pulled after giving up singles to Casali and Joey Votto in the seventh, and was replaced by Altavilla, who gave up a double to Suarez and walked Aristides Aquino, before surrendering the slam to Galvis.

Right-hander Tyler Mahle pitched just 3 1/3 innings and gave up four earned runs on eight hits and a walk, with six strikeouts. The Reds won for just the fifth time in Mahle’s 22 starts. Reliever Lucas Sims became the latest victim of Seattle rookie Kyle Lewis, who homered for the third time in as many games since debuting on Tuesday.