Unseeded Andy Murray won his first match, but he’s not crazy enough to think he can be a threat here and win his second U.S. Open.

Coming back from the hip injury that has wrecked his 2018 thus far, the 2012 Open champion rallied after losing the first set to win his first-rounder 6-7, 6-3, 7-5, 6-3 against 26th-ranked Aussie James Duckworth at the new Louis Armstrong Stadium.

Murray, who didn’t play Wimbledon because of lingering hip woes and played sparingly during the Open tune-up season, isn’t getting ahead of himself. He’s undergone three hip surgeries. Baby steps.

“I would have had to been able to train and practice a lot more than what I would have done and played more matches in the buildup to the tournament,” Murray said. “There’s many, many things I would have wanted to change to be considered a contender. I don’t think anything changes after today. It’s the first time I have played four sets in 14 months, so I just have to wait and see how I pull up tomorrow.”

Murray missed last year’s Open due to his hip troubles. He made headlines three weeks ago at the Rogers Cup in Toronto after finishing out a victory at 3 a.m. and weeping on the court. He later withdrew from the tournament.

When asked if his hip still has pain, Murray said that’s “still the case.” The Brit said he has rehabbed six hours a day as recently as last week after losing in the second round in Cincinnati.

“I actually felt I could have moved better,” said Murray, ranked 31st. “It was extremely lively conditions. I hit the ball a lot better than I did in Cincinnati. I’m not expecting to play my best tennis right now, actually.”

Murray played with his rebuilt hip and enjoyed the rebuilt Armstrong Stadium in its second official match.

“I think it looks great,’’ said Murray, who faces Fernando Verdasco next. “I think it’s a bit easier to play than the old Armstrong. It’s a little bit more sheltered from the wind. Before it used to swirl a lot in the old Armstrong. But this tends to blow in one direction. I think it’s a big improvement.”

Switzerland’s Stan Wawrinka, like Murray a former Open champion who missed last year’s event with knee injuries, got a wild card into the main draw. He made his tough-draw first match look easy, ripping the disinterested No. 8 seed Grigor Dimitrov 6-3, 6-2, 7-5.

The Bulgarian, long touted as a “NextGen’’ standout, committed 43 unforced errors to finish off a disappointing string of Grand Slam performances this year.

Venus Williams had a little hiccup in the middle of her match but ousted former Open champion Svetlana Kuznetsova in a three-setter, 6-3, 5-7, 6-3. She’s one win away from getting her sister, Serena Williams, in the third round.

John Isner’s pregnant wife is due to give birth in three weeks and a big run could cause conflict.

“I don’t control that — the man upstairs does,” Isner said. “Right now, we’re good.”

No. 1 seed Rafael Nadal advanced to the second round in abbreviated fashion when aging Spanish countryman David Ferrer retired despite being up a break in the second set.

Nadal had won the first set in tidy fashion, 6-3, but Ferrer was leading 4-3 in the second when he bowed out complaining of a calf injury. Ferrer, 36, has indicated this was to be his final major tournament.

“It was a gift playing center court with Rafa,” Ferrer said. “I’m sad because I can’t finish the match, but it’s not a problem. I’m a lucky man.”

It kept Nadal’s court time to 1:23 as he prepares for a second-round matchup with Vasek Pospisil of Canada, and got the Ashe crowd home at a reasonable hour.

To close out the inaugural nighttime card on Louis Armstrong, No. 3 seed Juan Martin del Potro, the 2009 champion and perennial crowd favorite, made quick work of one-time American wunderkind Donald Young, 6-0, 6-3, 6-4.