There will be neither boos nor cheers at the U.S. Open this year, because spectators were banned from attending the Grand Slam tournament. It is one of several measures meant to protect players and others on-site from getting — or spreading — the novel coronavirus. (AP Photo)

NEW YORK (AP) — The first time Kim Clijsters entered the U.S. Open, all the way back in 1999, she faced a certain someone by the name of Serena Williams.

All these years later, with play at Flushing Meadows set to begin Monday, three-time U.S. Open champion Clijsters is back on the scene, out of retirement at age 37 and entered in a Grand Slam tournament for the first time since 2012.

And Williams, less than a month from turning 39, is still at the top of tennis, the runner-up in New York each of the past two years and at four of the past seven major championships.

Asked to name a moment that sticks in her memory, Clijsters pointed to that first meeting against Williams, who won 4-6, 6-2, 7-5 in the third round and would go on to claim the first of her 23 Grand Slam trophies.

“It was an incredible match. The atmosphere was great. For me, that kind of, I think, started the energy that I feel here when I play here,” said Clijsters, who won the U.S. Open in 2005, 2009 (defeating Williams in the final) and 2010, along with the 2011 Australian Open.

“Any night match that you get to play here at the U.S. Open on Arthur Ashe is incredible,” she said. “It’s nothing like anything else anywhere else.”

As for Clijsters’ thoughts on Williams and the possibility of equaling Margaret Court’s total of 24 Slam singles titles?

“The great results she had, not even a year after her daughter was born — playing Grand Slam finals, competing for Grand Slam titles — was, I think, incredible,” Clijsters said. “Obviously, a lot of people talk about it. I think also for her, it gets harder to kind of not let it get to you, I think. She’s still working at it very hard, very passionate out there. That’s what we love to see. She’s a great competitor. Always has been that. You can only support that for somebody who has achieved so much and done so much.”

Here are other things to know:

CORONAVIRUS

The pandemic will loom over the two weeks. How couldn’t it? In April, indoor practice courts housed a field hospital. On Sunday, the first player, 17th-seeded Benoit Paire of France, tested positive for COVID-19. Players’ entourages are limited to three people. Everyone on the grounds must wear masks.

UNBEATEN DJOKOVIC

Novak Djokovic is 23-0 in 2020, the best opening to a season for a man since he went 41-0 in 2011. He’s also the only member of the Big Three in New York: Rafael Nadal and Roger Federer are not in the draw. That trio has collected the past 13 Grand Slam trophies in a row; that includes five of the last seven for Djokovic alone. “Whether I have a bigger chance to win it because Roger and Rafa are not here, I really don’t know,” Djokovic said. “I think it’s unfair for me to talk about. That, in a way, is kind of disrespectful towards other players who are here.”

HAWKEYE LIVE

There will be line judges only on the two largest courts. Everywhere else, a chair umpire will be assisted by electronic line-calling — removing the human element in the name of social distancing. Other concessions include: qualifying and mixed doubles were eliminated entirely; the men’s and women’s doubles fields were reduced by half; total prize money decreased.