The Mariners’ postseason hopes ended Thursday during their off-day in the Bay Area, but that didn’t mean Yusei Kikuchi didn’t have some work still to do.

Kikuchi closed out an inconsistent second season in Seattle with one of his best outings, firing six scoreless innings in a 3-1, 10-inning loss to the A’s on Friday at the Oakland Coliseum. The 29-year-old southpaw allowed four hits and walked three in a 99-pitch effort.

• Box score

Pinch-runner Dee Strange-Gordon scored on a passed ball in the top of the 10th to give Seattle a 1-0 lead, but the A’s won the game with three runs in the bottom of the 10th off rookie reliever Joey Gerber for their MLB-leading sixth walk-off win of the season. Mark Canha’s two-out, two-run homer to right was the deciding blow.

The Mariners were eliminated from postseason contention when both Houston and Toronto won on Thursday to take away long-shot hopes for the American League West No. 2 postseason spot and the league’s final Wild Card berth. At 25-32, Seattle now has just three games against the division-champion A’s left in this abbreviated season, including a doubleheader on Saturday.

Mariners manager Scott Servais felt Kikuchi took an important step in heading into the offseason on a positive note, in large part after adopting a more relaxed attitude in his finale. The lefty worked hard last winter to increase his velocity, and he appeared ready for a big season, but command issues tempered that performance for much of the season.

“It’s a matter of him understanding kind of where he’s at in his career and some of the adjustments he’s made mechanically,” Servais said. “His stuff has been outstanding, but it’s more than just that. You have to command the baseball and get it in the strike zone.”

Kikuchi finished the year 2-4 with a 5.17 ERA in nine starts. The former Japanese standout bounced back from his worst start of the season against the Padres with a strong showing against the A’s, whom he’d also held scoreless on three hits over six frames with nine strikeouts on Aug. 1. His ERA in his other seven outings was 6.94.

Kikuchi clearly is at his best when he lets things fly on the mound. He threw a complete-game shutout in Toronto late last season in that mode and seemed to have a similar approach against the A’s.

“It’s just kind of that fearless attitude, without getting too hyped,” Servais said. “That’s what excited me as much as anything tonight. I thought Yusei was very calm all night. Even when it looked like some of those innings might start to unravel, a couple guys on and nobody out, you keep pitching and grinding through it and executing, and I thought he did a very good job of that.”

Kikuchi acknowledged that he stayed more in control of his emotions on the mound and welcomed the positive note to his finale.

“I think it’s big,” Kikuchi said through translator Kevin Ando. “It’s something we had all talked about, just finishing strong and ending the year on a good note. I think I did a good job of mixing in my slider tonight as well and that will help me next year.”

The A’s had six doubles in the game, including three off Kikuchi, but the Mariners were able to work out of trouble until the 10th when Ramón Laureano drove in the tying run with his second double of the game and Canha followed with his 392-foot blast.

Seattle is now 11-22 in road games, compared to 14-10 in front of their own cardboard cutouts at T-Mobile Park.