Justin Dunn couldn’t find his fastball command on Sunday, but the Mariners found a way to pull out a 7-3 win over the D-backs anyway as a beleaguered bullpen pitched seven innings of two-run ball and rookie utility infielder Donovan Walton delivered three RBIs.

“That was a really gritty performance, is how I’ll term that game, by our whole team,” Mariners manager Scott Servais said. “End of the road trip, trying to end it on a positive note winning this series. We did a lot of really good things offensively and certainly our bullpen really picked us up today.”

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Walton, activated for the three-game series when shortstop J.P. Crawford went on the bereavement list due to a death in his family, ripped a two-run double in the sixth and also had a run-scoring grounder in the second.

“It’s amazing,” said Walton, a 26-year-old who played seven games as a September callup last season and was seeing just his third game as a taxi squad fill-in this season. “Getting a chance to come back in the big leagues and play with the big club again, all you try to do is anything you can to help the team win.”

Like all the players at the alternate training site, Walton has seen sporadic instrasquad action over the past two months and was 0-for-9 in his limited time with the Mariners before ripping his 412-foot double over center fielder Jon Jay in the sixth.

“He’s struggled a little bit,” Servais said. “They threw him a lot of offspeed pitches here and he hasn’t played much at all. But one thing about Donnie Walton, you talk about gritty. He’ll grind and is a competitor. That’s what he gives you every day. He’s always in the game mentally and was certainly looking for a pitch up that he could drive. He got one, and it may have been the biggest hit in the ballgame to create some separation there.”

How has Walton tried to stay sharp in this difficult season?

“It’s definitely different,” Walton said. “It’s been a thing to adjust to for sure this year, with everything going on. You just have to get used to it. Our hitting coaches here have done a great job of keeping me ready. I haven’t had the most at-bats this year, for sure. But going in mentally, it’s a brand new start of the season for me. That’s my mindset.”

Dunn would like a reboot of his own after his rough go against the D-backs. The rookie had been outstanding of late, going 2-0 with a 1.00 ERA and allowing just six hits over 18 innings in his three prior starts. But the 24-year-old right-hander couldn’t locate his fastball from the get-go on Sunday, and though he allowed just one hit, Dunn walked five batters while needing 66 pitches to get through two innings.

Dunn avoided a disaster by striking out five, including his final two hitters to wiggle out of a bases-loaded jam in the second. But his wildness forced Servais to go to the bullpen in the third.

“Just one of those days,” Dunn said. “I definitely think there was some mechanical [issues]. But the closest way to put it was that’s the way I felt in my [MLB] debut. I just wasn’t able to slow it down and get things under control. Luckily, I was fortunate enough to make a couple pitches in the second to get us out of that, or else it could have gotten ugly. I’m very thankful for that, but it wasn’t pretty.”

Seattle came into the game with the highest bullpen ERA in the American League, at 6.26, but Casey Sadler, Joey Gerber, Anthony Misiwicz, Kendall Graveman, Yohan Ramirez and Yoshihisa Hirano got the job done, as the Mariners closed out a 2-3 road trip and now sit 21-25 on the year, trailing the Astros by just two games for the second AL West postseason spot.

With a makeup doubleheader on Monday against the A’s in Seattle, the Mariners will need to lean again on their relief crew, as Servais plans to go with a bullpen game in the second contest. The club does have 11 relievers currently on its 28-man roster and can add a 29th player for the doubleheader. It will help as well that doubleheader games this season are just seven innings and the Mariners have their best starter -- Marco Gonzales -- going in the opener.

“That’s what we have to look at, and he’ll give us a real good effort,” Servais said. “After that, we’’ll have to piece it together. It happens. It’s a crazy season. Certainly, the day heading into a doubleheader, you’d like to get a little more length out of our starter. It didn’t happen, so we’ll have to adjust on the fly and that’s what we’ll do.”