On paper, it shapes as the ultimate tennis mismatch: a 21-times grand slam champion against an unseeded first-time major semi-finalist.
At one end, nine-times Australian Open winner Novak Djokovic, the owner of 92 career titles, $US164,786,653 ($A232 million) in on-court earnings and already many pundits' pick as the tennis GOAT.
At the other of Rod Laver Arena on Friday night will be 25-year-old Tommy Paul, the world No.35 with just one ATP trophy in his cabinet, $US3,721,250 ($A5.2 million) in prize money and a small regret of turning professional too soon instead of going to college.
But Djokovic is refusing to underestimate the underdog.
"Well, I know how he plays," the Serbian superstar said.
"I never faced him on the court. He's been around for a few years. I watched him play quite a bit, especially during this tournament. He's been playing probably tennis of his life.
"Very explosive, very dynamic player. Quick, very solid backhand. Likes to step in, dictate the point with the forehand. Great, great service motion.
"I think he can hit all the spots with the serve. Very complete player.
"He doesn't have much to lose. I'm sure he's going to go out trying to play his best tennis."
The first American to make the Open's last four since Andy Roddick in 2009, Paul says he's living the dream in Melbourne and the opportunity to play Djokovic on the big stage is win win regardless of the result.
"I'm really excited, man. It's really cool," he said.
"I saw him in the locker room after I finished my (quarter-final) match. He said 'congrats'. Not too much.
"We have practised before but we never played a match against each other.
"Obviously, he's pretty comfortable here in Australia. It's going to be a challenging match.
"But I'm playing some of my best tennis, so it's a good time."
Should Paul upset Djokovic, he would be the first American man to make the Australian Open final since Andre Agassi claimed his fourth title in 2003.
He's already guaranteed to be one of 10 US players to be ranked in the world's top 50 on Monday.
"That's all we've been hearing, since like 14 years old," Paul said. "The coaches have been telling us, 'We need new Americans, we need new Americans'. It's kind of engraved in my head.
"We all want to perform. Obviously Frances (Tiafoe) was pretty damn close at US Open to getting past the semis. Who knows what would have happened in the finals? I think we all want it pretty bad for ourselves, but we want it for US tennis, too."
The winner will play the victor of Friday's first semi-final between Greek world No.4 Stefanos Tsitsipas and Russian 18th seed Karen Khachanov for the title.
Tsitsipas is contesting his fourth sem'i-final in five years, losing the past two to Khachanov's countryman Daniil Medvedev.
Khachanov says he'll be no pushover after gaining much confidence from also reaching last year's US Open semi-finals.
"Sometimes when you have those great results, it shows you what you're capable of," he said.
"So you believe more and more."
