The Mariners got unexpected boosts from rookies Ljay Newsome and José Marmolejos on Thursday, but it wasn’t enough to hold off the Padres and they fell, 10-7, in the first game of a doubleheader at Petco Park in San Diego.

The Padres scored seven runs with two outs in the bottom of the seventh to pull out the win after Seattle scored four in the top of the inning. Per MLB rules this year, doubleheader games are just seven innings, but that was just enough for San Diego to come back twice from big deficits.

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Dee Gordon ignited a four-run rally in the top of the seventh with a leadoff bunt single, and rookies Sam Haggerty and Kyle Lewis and veteran Kyle Seager all contributed RBI singles. But the Padres scored seven times off relievers Taylor Williams and Dan Altavilla, with Wil Myers delivering a three-run walk-off homer to finish it off.

“That’s about as crazy of a last inning as you’ll see in quite some time,” said manager Scott Servais. “We did a lot of good things to put us in a great spot, we just couldn’t shut the door on a good team on the road. There were a lot of positives that will get swept under the rug there because we weren’t able to close it out.”

Williams had racked up six straight saves and worked his way into the closer role with a 3.00 ERA and 17 strikeouts in 12 innings over his first 12 appearances. But the Padres -- who had tied the score in the sixth on home runs by Fernando Tatis Jr. and Manny Machado off Matt Magill -- took advantage of a hit batter, two walks and then four straight hits to pull out the win.

The last two hits came off Altavilla, but it was Williams who took the loss and his first blown save.

“Sometimes you get in that spot and you want to be too good, a little too nasty,” Servais said. “He’s been awesome. Williams has been great for us in any role we’ve put him in. He didn’t have a great feel for the slider today. I thought he had enough to get through it, obviously it wasn’t quite enough.”

Newsome made his first Major League start as a late fill-in after Taijuan Walker was traded to the Blue Jays prior to the game, and the 23-year-old right-hander delivered four innings of one-run ball.

Newsome, who pitched three innings of one-run relief against the Dodgers in his only previous MLB outing, found out he was starting just about three hours before the game.

“That’s a great lineup and there’s nerves any time you go out there,” Newsome said. “But it’s good nerves.”

The Mariners’ No. 29-ranked prospect pitched most of last year at Class A Advanced Modesto before finishing up at Double-A Arkansas, but he’s proven fearless in his initial MLB outings and allowed just three hits with four strikeouts and no walks to the Padres.

“Ljay did a great job,” Servais said. “A ton of credit to Ljay. He is who is. He made pitches, he keeps throwing strikes and stays after them. I’m really happy with the effort he gave us today, and he’ll continue to learn. That’s his first start ever in the big leagues against a really good team. He did an outstanding job.”

Marmolejos, activated off the taxi squad as the extra “29th player” allowed for the doubleheader, helped the Mariners jump to a 3-0 lead with a two-run homer in the fourth inning. The 27-year-old was only in the game because first baseman Evan White hurt his right shoulder on a swing in his first at-bat in the second inning.

The loss snapped Seattle’s four-game win streak. The contest was postponed from Wednesday, when the Mariners voted unanimously to not play as a statement in support of racial equality and social justice in the wake of the Jacob Blake shooting in Kenosha, Wis.