MELBOURNE, Australia (AP)Ben Shelton’s concerns leading into his first Australian Open had less to do with playing tennis and more to do with everything else associated with the trip.

His first time outside of the United States. His first time using a passport. The jet lag. The time difference. The food. The driving on the left side of the road. And, oh, yeah, the whole part about keeping up with online classwork as he begins a new semester this week while pursuing a business degree.

Shelton, you see, is still just 20. A year ago at this time, he was attending classes and competing in college tennis at the University of Florida, where his dad, a former pro himself, coaches the men’s team. As of Monday, when he edged J.J. Wolf 6-7 (5), 6-2, 6-7 (4), 7-6 (4), 6-2 at John Cain Arena, Shelton is, suddenly and stunningly, a Grand Slam quarterfinalist – one of three American men to make it that far at Melbourne Park, the most for the country since 2000.

”Definitely a surprise. I got on the plane with no expectations,” Shelton, who won the 2022 NCAA singles championship, said of his performance at the second major tournament of his nascent professional career. ”It maybe has helped me a little bit, kind of not having that expectation or the feeling that I have to perform, but being able to just go out there, be myself and play free. I think that’s been a big contribution to my success.”

Now the 89th-ranked Shelton meets yet another unseeded American, 35th-ranked Tommy Paul, who eliminated No. 24 seed Roberto Bautista Agut of Spain 6-2, 4-6, 6-2, 7-5.

Their matchup will be the first Slam quarterfinal between two men from the U.S. since 2007, when Andy Roddick beat Mardy Fish in Melbourne. Roddick’s title at the U.S. Open 20 years ago remains the last major singles championship for a man from the country.

”It’s like every person’s dream when they start playing tennis to play the big matches at the Slams,” said Paul, a 25-year-old from New Jersey. ”I’m really excited to get out there on Wednesday. We know there’s going to be an American in the semis, so I’m really excited about that, too.”

Completing the trio is Sebastian Korda, who plays his quarterfinal Tuesday against No. 18 Karen Khachanov of Russia. Like Shelton and Paul, Korda has made it this far at a major for the first time. And like Shelton, Korda’s Dad played tennis: Petr Korda won the 1998 Australian Open.

There is nothing new about all of this, of course, for Novak Djokovic, the 21-time Grand Slam champion who looked indomitable during a 6-2, 6-1, 6-2 win over No. 22 seed Alex de Minaur of Australia and declared that his bothersome left hamstring is no longer an issue.

”I didn’t feel anything today,” Djokovic said, noting that he has been taking ”a lot of” anti-inflammatory pills.

Djokovic, who couldn’t play in last year’s Australian Open because he wasn’t vaccinated against COVID-19, moved a step closer to a record-extending 10th championship in Melbourne by never facing a break point and by claiming a half-dozen of de Minaur’s service games.

Djokovic moves on to a matchup against No. 5 seed Andrey Rublev. The Russian kept coming back, kept coming back, kept coming back – from down 5-2 in the fifth set, from facing a pair of match points while trailing 6-5, from deficits of 5-0 and 7-2 in the first-to-10 concluding tiebreaker – before finally putting away No. 9 Holger Rune 6-3, 3-6, 6-3, 4-6, 7-6 (11-9) at Rod Laver Arena.

Rublev won it when his backhand return slipped off the net cord and barely, just barely, made it over onto Rune’s side of the court, impossible to reach. Rublev dropped to his back at the baseline and raised both arms as if to say, ”Sorry!” – or perhaps ”Sorry. Not sorry!” – while Rune also flung away his racket.

”I have no words, man. I’m shaking,” said Rublev, who is 0-6 in Grand Slam quarterfinals for his career. ”That ball was exactly on my side and I don’t know how (it) went over.”

Advancing in the women’s draw Monday were Magda Linette – into the quarterfinals of a Slam for the first time at age 31 and in her 30th appearance at a major – Karolina Pliskova, Aryna Sabalenka and Donna Vekic.

Linette will play Pliskova, while Sabalenka will face Vekic for semifinal berths. On the other side of the bracket, it’ll be Jessica Pegula vs. Victoria Azarenka, and Elena Rybakina vs. Jelena Ostapenko.

Shelton and Wolf traded big cuts and momentum shifts on a day where the temperature rose above 80 degrees Fahrenheit (25 degrees Celsius).

The left-handed Shelton comes equipped with a powerful serve that produced the fastest offering of the tournament so far, at 142 mph (228 kph) during his first-round victory, an instinct for defense and a competitive streak. Against Wolf, who played college tennis at Ohio State and also was playing in the main draw in Melbourne for the first time, Shelton only faced two break points and saved them both.

At times a bit quiet in the early going under the sun, Shelton grew more and more loud and animated as the shadows crept across the blue playing surface and the scoreline increased the intensity.

He would throw uppercuts and yell, ”Come on!” or ”Let’s go!” after winning points, and when the close contest came to a close, Shelton jutted out his tongue and flexed his arms.

”Each match that I’ve won here has felt the same. It’s a mixture of joy, relief. I just have that feeling of ecstasy, right? When the last ball lands: `I did it!”’ Shelton said. ”To be able to do that on this stage four times in a row, that feeling over and over again, has been pretty cool.”

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