OPEN & SHUT OUT

AMERICAN men competing at the U.S. Open have been almost equally out of sight ass out of mind. Yes, Jack Sock got the opening-night match at Louis Armstrong Stadium on Wednesday, but at the same time Serena Williams was on court at Arthur Ashe Stadium.

Otherwise, the Yanks have been outsiders. John Isner, the 11 seed who beat Nicolas Jarry 7-6, 6-4, 6-3, 7-6, 6-4 Wednesday, has played two lateafternoon matches on the Grandstand. Frances Tiafoe, the engaging 20-yearold, is scheduled for his secondrounder on Court 17 late Thursday afternoon after having won his opening match on the Grandstand.

And Taylor Fritz, the 21-year-old young gun who rallied from two sets down to beat Mischa Zverev in his first-round match on Court 10 on Monday morning, was in the Court 13 steam bath for Wednesday’s second-round 6-3, 3-6, 6-3 (ret) victory over Aussie Jason Kubler that was contested in front of a small circle of friends.

Longing for the old days in which John McEnroe, Jimmy Connors, Andre Agassi and Pete Sampras all but monopolized the spotlight here decades ago is akin to longing for the time that Joe Namath was running things for the Jets. They are history and they are not coming back.

But it might serve American tennis if the best and brightest young Yanks were featured in the early rounds of the competition rather than being shunted to the perimeter. Of course, the corollary argument can be made that the marquee is not bequeathed by birthright, but rather is reserved for those who earn it by performance.

Constructing a schedule that serves varied competing constituencies is no easy task. The Open and the USTA’s broadcast partners must be served. No one is naïve enough to believe that a Fritz or Tiafoe could draw more than a relatively small fraction of the eyeballs that are drawn to watch a Roger Federer, Rafael Nadal or Juan Martin del Potro. The Open may represent a two-week wonderland of entertainment, but there is no mistaking that its first business is business.

Still, tournament director David Newman told The Post on Wednesday that, “Giving visibility to young and upcoming Americans is absolutely a consideration.

“But at the same time you have to realize that this is a global event.”

And Federer is the de facto favorite son.

America has not produced a men’s Open champion since Andy Roddick in 2003. Roddick is the last American to reach the semis, in 2006. Roddick and Isner were the last two to reach the quarterfinals, in 2011.

Or as USTA general manager Martin Blackman said early Monday morning, “There’s always a sense of urgency on the men’s side. Obviously we have a long way to go.”

There is a long way from Court 13 to Ashe Stadium, but Fritz took steps in that direction with his victory over the Aussie qualifier, who was forced to retire after rolling an ankle in the second set. This represents the first time in the Californian’s career that he has advanced to the third round of a Grand Slam event.

“It’s not the way you want to be in the third round, I’m not as happy as I would be if I won it without my opponent retiring, but I do feel that I worked really hard and deserve it,” said Fritz, who collected 30 winners but committed 27 unforced errors. “I’m excited for my next match.”

The next match comes against ninth-seed Dominic Thiem, the 24-year-old Austrian who knocked Fritz out of last year’s tournament in Round 2.

“As a young guy, I’m definitely looking to compete against the best players in the world and kind of earn my spot and show people I [belong] with those types of players,” Fritz said. “We had a really close match last year, I had tripleset point to take it to a fifth and I’m a much better player than I was last year. So I’m excited for the match.”

Fritz, whose mom, Taylor May, reached No. 10 in 1977 and the Open quarters in 1978, pointed to improved conditioning as a prime factor in his development. His conditioning was an asset in the sweltering heat.

“The heat is part of what we train for. I think playing in this heat shows who’s fit and who’s not fit,” he said. “I think fitness is part of the sport and playing five sets is one of the ultimate tests in sports for how fit you are.”

The question now is whether the powers that be believe that Fritz is fit for a close-up on Ashe.

Getty Images (2) OUTSIDE LOOKING IN: American John Isner, despite being ranked No. 11, had yet to play anywhere bigger than the Grandstand, as U.S. men had been kept out of the Open’s two biggest venues, Louis Armstrong Stadium and Arthur Ashe Stadium.