Jordan Montgomery didn’t have the game ball from his first win, and he wasn’t sure if anyone had put it aside. The family members who came to see his first major-league start last Wednesday had to head home and weren’t there. They had jobs to go to and lives to live, and Montgomery didn’t seem to mind at all.

As he sees it, if he has his way, there’ll be plenty more games to celebrate.

“I try not to make a big deal of it,” he said Monday night after leading the Yankees to a 7-4 victory over the White Sox at the Stadium, their eighth straight win. “It’s just a game, hopefully the first of many.”

There’s a quiet poise there that’s almost unnerving in someone who supposedly is so green. When two batters got on against him in the first inning, the lefty never seemed shaken. After he allowed a three-run home run by Yolmer Sanchez in the seventh, he went back to the dugout and never hung his head, Joe Girardi said. He gave up seven hits, three in the seventh, with two walks and four strikeouts.

“I’m just focused on the first six [innings],” he said. “I still made pitches and executed and just didn’t make one. We won. Team win and roll from here.”

His attitude on and off the mound portends good things for this Yankees team, which has ridden its starting pitching and bullpen to the longest current winning streak in the majors. They’re still undefeated (7-0) at home, and that’s with their starting catcher and shortstop on the disabled list and with an offense that has struggled to hit with runners in scoring position.

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Until Monday night, that is.

While Montgomery cruised, the lineup did an admirable job of backing him with a five-run third inning that included a three-run moon shot by Matt Holliday. The home run — an estimated 459 feet — was so long, it could have knocked the cheese off a nacho. Well, sort of.

“He probably ruined some family’s dinner,” said Aaron Judge, who hit a two-run homer in the fifth. “They probably got some nachos. He probably hit that ball so hard, it knocked it out of their hands. That was a great swing by Matty.”

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The Yankees, who came into the game hitting .200 with runners in scoring position, went 3-for-7 in that situation Monday night, all in the first three innings.

After Holliday’s home run, Starlin Castro doubled to center and Chase Headley brought him home with a double to left that was misplayed by Tim Anderson to land Headley on third. That cost the White Sox another run as the next batter, Judge, legged out an infield hit to give the Yankees a 5-0 lead.

Montgomery showed all the traits that earned him a roster spot in spring training. He turned to his sinker to help get out of the second and fourth. He got Kevan Smith to ground into a 6-4-3 double play in the second and worked around Melky Cabrera’s leadoff single in the fourth, thanks to Avisail Garcia’s double-play ball. He allowed back-to-back singles in the seventh before Sanchez’s home run.

Adam Warren, who relieved Montgomery in the seventh and extended his streak of batters retired to 22 before allowing a walk, gave up a long RBI double to Smith in the ninth. Aroldis Chapman got the final two outs for his fourth save.

“I think he does have a lot of poise,” Girardi said of Montgomery, noting his start in the College World Series as a South Carolina freshman. “I know it’s not pitching at Yankee Stadium, but pitching in the College World Series is a big deal. There’s a lot of pressure and a lot of emotions, and he had been through that and I felt that would help him.”

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Montgomery was asked how much he thinks about that college game. Not much, he said. “It’s pretty similar” to pitching at Yankee Stadium. “Granted, I was 17 years old when I was doing that. The big stage played up even more then. I think I’m a little more mature.”

A lot more mature, apparently, if the biggest stage of all doesn’t faze him.