BOSTON — For the Red Sox, bouncing back from their rough start coming out of the All-Star break has to start somewhere.

Why not a walk-off win to cap a tense Wednesday of baseball at Fenway Park in a rubber match against a team they are fighting with for position in the American League Wild Card race?

Rafael Devers delivered the winning blow against Mariners lefty Jhonathan Diaz, a leadoff double off the Green Monster in left-center to deliver automatic runner Tyler O’Neill from second to give the Red Sox a 3-2 win in 10 innings.

Devers delivered Boston its first winning series in four tries since the All-Star break. It was the third walk-off hit of the star slugger’s career, and first since June 14, 2021.

With first base open, it was natural to wonder if Devers would get walked intentionally.

But the Mariners were running out of relievers, and Diaz was the guy that manager Scott Servais went to. With lefty destroyer Rob Refsnyder on deck, Devers got a chance to hit.

And on a 2-0 pitch, he got enough of it to drive it off the wall and end the game.

“When they brought in the lefty, I knew they were going to pitch to me with a righty behind me,” Devers said. “I knew that was going to hit the wall. I hit that ball well, but not as good as I wanted to.”

When the Red Sox look back at Wednesday’s triumph later in the season, it might wind up being an example of how all wins aren’t created equal during a baseball season. With this one, Boston (57-50) snapped out of a 3-8 rut and won the season series against a Seattle team it is jockeying for position in the Wild Card standings, though the Mariners (57-53) currently lead their division.

How big was this win for the Sox, who ride into Thursday’s off-day with at least some momentum?

“We’ll know Friday, right?” said Red Sox manager Alex Cora. “Today was a grinder for all of us, for them, too. To end up winning, it was great. Some guys had to do a little bit more.”

One of those people who had to do more was Zack Kelly, who had given up six hits, five earned runs and three homers in his five outings since the All-Star break.

But after a shaky outing that contributed to Boston’s 10-6 loss on Tuesday, Kelly rebounded on Wednesday, working out of a bases-loaded, two-out jam in the top of the 10th.

“[Felt] so good,” Kelly said. “The last few outings have been pretty tough mentally. Today was good. Needed that one. Feel like a clean slate and now we go.”

It’s always interesting to see how trade acquisitions perform in the days immediately following the Deadline.

So there was Danny Jansen – who made his debut with his new team as the DH on Sunday – catching a 10-inning game on Wednesday with a pitching staff he had never worked with before. And it was also Jansen who found a hole on the right side with a clutch, RBI single to tie the game with one out in the sixth.

“It was great,” he said. “Looking to help anyway I can and get a pitch to get him in and happy it was a fastball away and I shot it through the four-hole.”

And there was reliever Lucas Sims, in his first day on the active roster a day after being acquired, coming on with runners at the corners and one out in the top of the seventh with the game tied.

Sims got Randy Arozarena on a flyout to right, not deep enough to get the run in. And after walking Cal Raleigh to load the bases, he got a hitter known for his clutch gene in Justin Turner to ground out to third.

“I live for moments like that,” Sims said.

In the midst of what should be a tight race the rest of the way, the Red Sox – who trail the Royals by two games for the third Wild Card spot – should have their share of big moments ahead. Before getting to those, they will enjoy Wednesday’s ultimate accomplishment – which was just finding a way to win.

“It’s a good one. It feels like a relief, to be honest with you,” Cora said. “It was a grind the whole day. It was a little bit hotter out there and every pitch mattered. To win the series, it feels good.”