The two players bring a combined 28 Grand Slam titles to the first night of the U.S. Open. That’s unprecedented for a first-round match.

But whether Monday’s under-the-lights Serena Williams-Maria Sharapova superstar showdown at Arthur Ashe Stadium lives up to the drama is questionable.

Williams is trying to put the past behind her. Sharapova, 32, is trying to find her past.

Williams, 37, returns to the scene of last September’s emotional blowup against Naomi Osaka in the Open finals. She skipped the Open’s media day and has not commented on the marquee match or her latest chase to tie Margaret Court’s Grand Slam record of 24.

“I think her opportunities are running out,’’ said Chris Evert, ESPN’s top voice for women’s tennis. “I think this and maybe the Australian Open could be the last two.”

Though Williams suffered back spasms in Toronto this month, a photo posted on social media of her doing a cartwheel over her sister Venus in a gym session should clear up whether she’s fit. The video was titled “Flipping into The Open.’’

Sharapova, according to tennis insiders, is not so fit and stands as a big long shot. The right shoulder that was operated on 10 years ago still is bothering her and she’s also had forearm issues. Eventually Sharapova will need another shoulder surgery, but that likely will come after retirement, according to sources.

Sharapova took six months off to heal, returning in late June, and her ranking has dropped to 87.

In the Open tuneups, she lost a first-round three-setter to 16th-ranked Anett Kontaveit in Toronto, and in Cincinnati was beaten in the second round by the Open’s No. 2 seed, Ashleigh Barty.

That came after a forearm issue caused Sharapova to retire at Wimbledon in the third set of her first-round match. It was the first retirement of her career in a Grand Slam event.

Meanwhile, Serena lives to beat Sharapova, holding a 19-2 record against her. Years ago, Serena’s camp was jealous of the amount of endorsements Sharapova racked up despite achieving less on the court than the Williams sisters. Sharapova won two of the first three meetings, but it’s been all Serena since.

But a veteran like Sharapova, who has won five Slam titles including the 2006 Open, can’t be discounted. She is a warrior, having made the most of her limited athletic ability because of a fierce competitive spirit.

The hope from Sharapova’s camp is if she can keep it tight late in the first set, perhaps Williams will get tight with all the pressure on the 23-time Grand Slam champion attempting to make history.

The tennis community is buzzing about perhaps the highest-profile first-round women’s match in Open history.

As defending champion Osaka said, “I’m going to set my TV timer so that I can watch it.”

Serena has had sparse match preparation since getting blasted in the Wimbledon finals in July by Simona Halep. She’s won six Open titles, but is in a championship rut since returning to the tour in the spring of 2018 after giving birth to her daughter.

Her schedule has been scaled back since becoming a mother. After suffering back spasms this month in Toronto, forfeiting mid-match, Williams withdrew from the final Open prep in Cincinnati.

She could just be saving herself for the last Slam. Williams has reached the finals of three of the six majors she’s played as a mom, but has gone 0-for-3.

“When you don’t have time to train as much, even if you have the résumé, confidence is everything,’’ Serena’s first coach, Rick Macci, told The Post. “Maybe the players she plays aren’t as intimidated.”

Still, Evert thinks Serena could well get off the Slam schneid here.

“I just have a lot of belief in Serena,’’ Evert said. “I’ve just seen her come back from adversity so many times in the last 20 years.

“The one added component that she has now that I probably overlook is age and injuries. Even though she looks unbelievable when she plays, to play like that for seven matches is a tough task to ask a [soon-to-be] 38-year-old, very much like a Roger Federer. I still feel she has the highest ceiling of all the players.”