Defending champion Carlos Alcaraz and 23-time Grand Slam winner Novak Djokovic are one victory away from a blockbuster US Open final showdown as they head into the semi-finals at Flushing Meadows on Friday.

The dream final that every tennis neutral wants to see moved a step closer to reality on Wednesday as Alcaraz dispatched 12th seed Alexander Zverev with a ruthless 6-3, 6-2, 6-4 victory in less than three hours.

The 20-year-old Spaniard will face Russian third seed Daniil Medvedev in Friday's semi-finals, a player he has already beaten convincingly on two occasions this season.

On the other side of the draw, Serbian second seed Djokovic -- who will take over from Alcaraz as world number one at the end of the tournament -- faces unseeded American rookie Ben Shelton, the big-serving surprise package of the tournament.

On current form, Sunday's men's singles final at the Arthur Ashe Stadium looks certain to serve up another instalment of the nascent rivalry between Alcaraz and Djokovic, two months after their five-set Wimbledon final classic won by Alcaraz.

Certainly, that was the belief of an exhausted Zverev following his defeat to Alcaraz on Wednesday. Zverev says the duo are simply on another level to the rest of men's tennis. 

"I played Novak in Cincinnati, I played Carlos here," Zverev said. "I think they are very, very similar from the level of the game.

"There are some things that Novak does better; there are some things that Carlos does better. They are at a level of their own at the moment. The other guys gotta catch up."

Medvedev, who showed great resilience in overcoming ferocious heat on Wednesday to defeat Andrey Rublev in straight sets, says that Alcaraz will require him to raise his game to another level.

"I'm someone who fights a lot, so I want to try to be better, and I need to be 11 out of 10 to try to beat him," the Russian said.

- 'He has every shot' -

Medvedev is under no illusions about the difficulty of the task awaiting him in facing a player that combines breathtaking variety of shot-making with raw power.

"What makes him difficult is just that he has every shot," Medvedev said of Alcaraz. "He has extra power to other players." 

Yet Medvedev, who famously upset Djokovic in the US Open final two years ago to deny the Serb a long-sought after calendar Grand Slam, knows as well as anyone that upsets can happen.

"Tennis, you can always beat players," Medvedev said. "People beat Novak. People even beat Rafa (Nadal) on clay, which is almost impossible, but some players do."

Alcaraz meanwhile admits it would be "great to play a final against Novak here in New York", but is keeping his sights firmly focused on Friday's last-four date with Medvedev.

Alcaraz believes he is now a stronger player than the teenager who lifted his first Grand Slam title at the US Open a year ago.

"I'm more mature now," Alcaraz said. "I grew up a lot since last year. Last year I was facing my first semifinal of a Grand Slam. Now I'm facing my fourth one.

"I feel like I'm a totally different player. I deal better with the pressure with that kind of moments. I feel like I'm a different person and different player."

While Alcaraz believes he has improved, the 36-year-old Djokovic has remained his old, formidable self in New York, driven by a relentless hunger for success in what is surely the twilight of his playing career.

"Things are different when you're 36," Djokovic said on the eve of the tournament. "I have to be more appreciative, treating every Grand Slam as maybe your last one."

Djokovic's quarter-final rout of American ninth seed Taylor Fritz sent him into an incredible 47th Grand Slam semi-final, putting him one clear of Roger Federer for the all-time men's record. In his last 27 Grand Slam semi-finals, Djokovic has lost just twice.

Yet while the odds are stacked against him, Shelton, 20, believes that he can bring an element of surprise to what will be his first meeting with Djokovic. 

"Whenever you play somebody for the first time and someone who has been in this situation so many times and come out victorious so many times, that's in the back of your head," Shelton said. "You just know how rock solid the guy is and how mentally tough, how physically tough.

"I also think that, you know, it's an advantage with my game style playing someone who's never played me before. 

"I'm definitely going to try to bring some things to the table that are different and hopefully disruptive on Friday."

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