NEW YORK -- The difference between the Mariners at the start of the season and the Mariners that became the hottest team in baseball over the past two months is clear, according to manager Scott Servais.

With a more balanced lineup and offensive production that finally mirrored its potential, Seattle rattled off series win after series win, tallying 12 in its last 13 tries and five in a row entering Sunday’s critical rubber match at Citi Field.

“We are more capable of coming back, we’re hitting the ball out of the park, we’re creating opportunities, we’re more balanced left-right,” Servais explained before the game. “We still have our issues at times … but the vibe around our team is much more, ‘Hey, we can get this done. We can come back.’”

That was the task facing the Mariners on Sunday afternoon, but they weren’t up to it in the finale, suffering a 6-3 defeat to the Mets and their first series loss since the Aug. 11-13 set against the American League East-leading Orioles. Seattle (77-59) maintained a one-game lead over the Rangers (76-60) and Astros (77-61) in the AL West standings.

• Games remaining: at CIN (3), at TB (4), vs. LAA (3), vs. LAD (3), at OAK (3), at TEX (3), vs. HOU (3), vs. TEX (4)
• Standings update: The Mariners are one game ahead of the Astros and Rangers for the AL West lead. Seattle is currently the second-best division leader, meaning it would host a five-game AL Division Series vs. the winner of a Wild Card Series starting on Oct. 7.

It was the Mariners’ first loss by three or more runs since July 19, when they fell by the same 6-3 score to the Twins. They went on to split that series, following a series loss to the Tigers; those are the only other times that Seattle hasn’t earned a series victory since the All-Star Game on July 11 at T-Mobile Park.

“It happens. You do lose series once in a while,” Servais said after his club fell to 8-10 in rubber games this season. “They played very well, and they handled our pitching. Normally, our pitching kind of gets it going and can take over the course of the series, but in this series, we didn’t do it.”

With George Kirby on the mound for the first time since Aug. 23 after being scratched from his last scheduled start with an illness, the Mariners fell into a 4-0 hole three innings in, highlighted by Pete Alonso’s 40th home run of the season. It was part of a two-homer, four-RBI showing for the Mets’ cleanup hitter.

The Nos. 6-7 batters in Seattle’s order, Dominic Canzone and Mike Ford, brought the Mariners within one run with back-to-back homers to nearly the same spot beyond the right-center-field wall in the fourth, but the bats didn’t have any more juice after that.

Kirby, a Rye, N.Y., native who had family and friends in attendance for his second career start against the Mets at Citi Field, exited after three innings, marking his shortest outing of the season. It was the same type of uncharacteristic performance that hurt AL Cy Young Award challenger Luis Castillo on Saturday, though J.P. Crawford ensured that Seattle still came away victorious that time.

“They swing a lot,” Kirby said. “I have that problem sometimes living in the zone a lot; some guys just swing aggressively. So I’ve got to do a better job just getting under the zone and getting them to chase. But they’re a good team.”

Crawford had a chance to be the hero once more on Sunday, coming to the plate as the tying run with two men on and two outs in the ninth. But this time, Mets right-hander Adam Ottavino got the better of Crawford, striking out the shortstop swinging on a 94 mph fastball.

It proved to be one comeback too many for the Mariners, for whom the road only gets tougher from here, with series against the Reds and Rays -- a pair of teams firmly in the NL and AL Wild Card chases, respectively -- coming up next.

In that sense, the weekend set in New York was a missed opportunity for Seattle to capitalize against lesser opposition, though the Mariners don’t entirely see it that way.

“Even the teams that are below .500 are teams that play us very tough. There are no easy ones there at all,” Servais said before the game. “And that’s the way it is in September when you have a chance to get into the playoffs. So I’m not surprised by it, our players aren’t surprised by it. But we just need to keep looking forward. Don’t look behind. Look forward.”