SEATTLE -- The Padres’ chance to separate from the pack in the final weeks of the regular season continues to stop and start.

San Diego lost the capper of its two-game jaunt to Seattle, 5-2 to the Mariners at T-Mobile Park on Wednesday night. The loss, coupled with the D-backs’ 14-4 win over the Rangers, moves San Diego a half-game behind Arizona for the top National League Wild Card spot.

“They’re winning, and so are we,” said right fielder Fernando Tatis Jr., who hit a home run and robbed one in the same inning. “We’ve just got to keep playing the way we have and keep our heads up, with the winning mentality this team has had all year.”

The tiebreaker between San Diego and Arizona is undecided, and won’t be settled until the Padres’ three-game set at Chase Field to end the regular season. San Diego sits 1 1/2 games ahead of the Mets, who occupy the final playoff position, with another game of breathing room ahead of the Braves.

Fifteen games into an 18-game stretch against teams currently on the outside looking in of their respective playoff hunts, San Diego has gone 8-7. After an off-day Thursday, the Padres will open a three-game set in San Francisco. Following that, three of San Diego’s final four sets are against teams currently sitting in playoff spots.

Seattle’s Bryan Woo started the night by retiring the first 19 batters he faced before Tatis broke up the perfect game bid with a solo home run to left field with one out in the seventh inning.

“I saw him being aggressive, and I told myself I had to be more aggressive than him,” Tatis said. “After the first round, I didn’t see him throwing many breaking balls. So the third at-bat, I went up really confident, looking for the fastball.”

Tatis indeed got two fastballs to start off his third at-bat, taking the first before turning on Woo’s 1-0 offering -- a 94.8 mph heater well off the inside corner -- and driving it out at 115.6 mph, his second-hardest hit this season.

“That was an impressive swing, just boom, right down the line,” Padres manager Mike Shildt said.

Tatis finished the quick two-game set in Seattle with a pair of home runs -- his first two since returning from the injured list on Sept. 2 -- and three total hits, after going 5-for-24 in his first five games back.

His highlight reel didn’t end in the top of the seventh inning. In the bottom half of the frame, Randy Arozarena belted a high fly ball that flew over the wall in right -- only for Tatis to bring it back.

“I saw it off the bat and I knew it was going to be a close one, and let my abilities play,” Tatis said.

On one hand, the September stretch run isn’t the time to pull minor victories and highlights out of losses. On the other, a full-strength Tatis, hitting like a two-time Silver Slugger and playing defense like a Platinum Glover, is the sort of weapon that could single-handedly swing a postseason race down the wire.

“That just tells you how talented he is and what he’s capable of, so that’s a really good sign for us,” Shildt said. “... Holy cow, what a player.”

Padres starting pitcher Michael King allowed three runs (one earned) on four hits in five innings. He struck out six.

The one blip on King’s night came in the third inning. After walking a batter and hitting another with one out, King got Julio Rodríguez to hit a sharp ground ball to the left side of the infield. Xander Bogaerts, starting at shortstop for the second night in a row, took a step to his right to field it and threw to Jake Cronenworth at second, but Cronenworth couldn’t corral the feed.

The drop was originally ruled on the transfer, but after review the call was overturned, loading the bases with still one out.

Cal Raleigh made the Padres pay for the error three pitches later, chipping King’s 1-1 changeup into right for an RBI single. A batter later, Seattle made it 3-0 on a two-out, two-run single by Luke Raley that brought what turned out to be the game-winning run home.

Seattle’s other two runs came in the sixth, when Adrian Morejon began the inning with back-to-back walks, both of which came around to score.

“We had three walks and a hit batter all score, and of course we didn’t help ourselves with the defense,” Shildt said. “Very, very uncharacteristic of us.”