“Of course, it’s [an] unbelievable feeling … first time playing main draw, first time [making] semis, it’s incredible,” said Karatsev, securing victory in two hours and 32 minutes to guarantee a minimum prize money cheque of at least $A850,000 ($US662,000), more than his total career winnings of approximately $US618,000.

“It was really tough from the beginning for me to hold the nerves … I tried to find a way and then in the third he felt the back,” said the Russian, who had already earned bragging rights as the lowest-ranked player to reach the final eight in Melbourne in 30 years. 

With the victory, Karatsev becomes the second qualifier to reach the last four at the Australian Open, and just the fifth qualifier to reach a major men’s semifinal at a Grand Slam in the Open Era. Tuesday’s win was his fifth at Australian Open 2021; he entered the tournament with just three ATP-level victories since 2015. 

With the victory, Karatsev becomes the second qualifier to reach the last four at the Australian Open, and just the fifth qualifier to reach a major men’s semifinal at a Grand Slam in the Open Era. Tuesday’s win was his fifth at Australian Open 2021; he entered the tournament with just three ATP-level victories since 2015. 

The Bulgarian began the second set in an easy rhythm, manufacturing a quintet of break points in a marathon second game, which the Russian did well to fend off. Ever the aggressor, the 29-year-old Dimitrov pressed in the fourth game but again was unable to convert two break points as a trio of aces allowed Karatsev to hold for 2-2. 

Dimitrov then sent a forehand approach long to donate a break to his opponent but the Russian quickly served up a double fault to hand the 18th seed the break back for 3-3. 

In the ninth game, Dimitrov saved one break point with a squash-like chopped forehand return but capitulated on the second as Karatsev steered a backhand winner down the line, celebrating the break with a roar. The upstart calmly held to love to capture the set 6-4.

A pair of double faults to start the third set didn’t initially derail AO 2017 semifinalist Dimitrov, but the qualifier played an impeccable return game, striking a sizzling backhand cross-court winner to break for 2-1.

Karatsev hit the repeat button, producing four winners en route to securing a double break, consolidated and broke again to steal the third set 6-1 as the Bulgarian’s physical discomfort became evident.

A medical time-out for off-court treatment prolonged Dimitrov’s ability to fight on, but the Bulgarian – who was stretching between points – blinked first in the fourth set to give up a break in the fourth game. Focused on the finish line, Karatsev sealed match point with a backhand winner, earning the victory despite an unforced error count that crept up to 44, 10 more than Dimitrov.

With the win, Karatsev set up a first-time meeting against the winner of Tuesday night’s blockbuster quarterfinal between eight-time Australian Open champion Novak Djokovic and sixth seed Alexander Zverev.

“I try not to think about it, I try to play every match going from match to match,” smiled the Russian world No. 114, who is the lowest-ranked man to reach the semifinals at a major since No. 125 Goran Ivanisevic at 2001 Wimbledon.

Dimitrov, explaining that he'd developed a back spasm the day before the match, said Karatsev "absolutely deserved" his victory. 

"I'm almost sure that it's not like a massive injury or anything like that, but it just requires a lot of specific work and staying away from the court for a little bit," said the 18th seed, who remained upbeat despite the circumstances.

"I'm just going to take the positives out of this situation ... today was just bad luck.

"I don't need to dwell on the situation."

Katatsev - who is now set to achieve his 2020 goal of cracking the top 100 - said he'd received around 200 messages of congratulations from friends and family. The Russian credits his coach, former Belarusian player Yahor Yatsyk, for improving both the technical and mental aspects of his game. 

"I try to believe every match [in] what I'm doing on the court, and it's helped me to win matches," he said.

- AusOpen