SEATTLE — James Paxton came to the Yankees to win. Bottom line.

That is what the left-hander is doing on a consistent basis of late. A big reason for that success is the decision to throw his back-door curveball more, which sets up his other pitches.

Paxton won his sixth straight start Wednesday and this one came with the added pleasure of beating his former team as the Yankees slugged their way to a 7-3 victory over the Mariners on a perfect summer’s day at T-Mobile Park to give the Yankees a three-game sweep.

Paxton moved to 11-6 his first year as a Yankee. The next victory for Paxton will match his career high, set in 2017 when he went 12-5 with a 2.98 ERA for the Mariners.

It is a good life, pitching for the Bronx Bombers. There is room for error. Until the postseason.

“These guys make it easier on me when they are scoring this many runs,’’ Paxton told The Post. “It’s awesome. The ultimate goal is getting the team a win. I try to put my best foot forward to help do that. It feels good to be in the place I’m at right now and go into the postseason in a good place.’’

Getting to that place is in part due to the use of his curveball. He said he made the adjustment earlier this month.

“It’s something that slows guys down because my other two pitches are hard, the fastball and the cutter, so it gets them off-balance a little bit and it makes them slow their swing down and respect something on the outer half,’’ Paxton said. “The curveball plays really well off my high fastball. It gives them that little hesitancy.’’

Paxton matched up against lefty Justus Sheffield, 23, a key piece of the trade that brought Paxton, 30, to the Yankees. He won the battle as the Yankees got a monster two-run home run from Gary Sanchez in the first and two more home runs in the fifth from Mike Ford and Aaron Judge, who completed his West Coast Home Run Tour. DJ LeMahieu homered in the ninth.

Paxton lasted just five innings because of a loss of command at the end of the second inning and start of the third when he walked five of seven batters. Sanchez bailed him out by throwing out two runners at second attempting to steal.

Paxton allowed only one hit, a two-run home run by Kyle Seager in the fourth inning.

Paxton came into the afternoon a road warrior when it came to control. Over his previous four road starts, he struck out 38 batters and walked one.

Paxton is figuring out what works best on the mound.

“This game showed what I could accomplish with lesser stuff,’’ he said.

And there were a little bit of nerves facing his old team.

“It was definitely weird for sure, a new experience, facing a team I was with for such a long time,’’ Paxton said. “I tried not to think about it and was just going out there and do what I do.’’

Judge believes the Big Maple is really starting to blossom and went so far as to say, “He’s the best left-handed pitcher in the game with the type of stuff he has. He has a great curveball, a great cutter and is getting the fastball up to 98-99. He is just now starting to trust that [stuff] and that is the biggest thing. It’s different playing in New York and now we are seeing that he is just starting to pitch like Paxton.’’

Paxton’s six straight victories come after a run in which he did not get a win over six straight starts, with three no-decisions and three losses.

It is a much different world now for Paxton.

The wins are piling up for him and the Yankees. He needs to keep it going and the Yankees need for him to continue to figure out ways to win.

With Masahiro Tanaka throwing seven shutout innings on Tuesday and Paxton getting the win Wednesday, Yankees starters are sitting on four straight wins for only the second time all season.