Comparing careers, Grigor Dimitrov – the one-time world No.3 and 2017 season-ending champion – should stop Alex de Minaur’s bold US Open run on Monday morning (AEST).

But scratch the surface and it’s clear de Minaur is a hot favourite to back up his electrifying win over Kei Nishikori and set up a quarter-final showstopper with Roger Federer.

Dimitrov is a shadow of his old self, slumping to 78th in the rankings after a dire 2019 season featuring more losses than wins.

The fallen force won just one match between the French Open and arriving in New York, a crisis of confidence leading to five first-round defeats, the most forgettable a humbling straight-sets loss to world No.405 Kevin King in Atlanta – where de Minaur landed his second title of the year.

An Australian Open semi-finalist only two years ago, Dimitrov has needed a major leg-up to reach the last 16 at Flushing Meadows.

He needed four sets to get past 35-year-old Andreas Seppi in round one, received a walkover in round two and was unconvincing in a third-round win over qualifying lucky loser Kamil Majchrzak.

Now the Bulgarian’s dream draw is over, according to de Minaur’s countryman Nick Kyrgios.

“De Min, he’s an absolute warrior. He can beat a lot of good players. When I see him progressing through a draw, I know it’s a nightmare for anyone who comes across him,” Kyrgios said.

De Minaur, though, is taking nothing for granted, promising only to leave it all out there in his bid to gatecrash the quarter-finals at a grand slam for the first time.

“I’ll take it as a big opportunity,” the 20-year-old said.

This is where I want to be, so I’ll go out there and leave 100 per cent. Nothing changes.’’

Victory over Dimitrov and a ninth win for Federer from 10 clashes with David Goffin would thrust de Minaur into a dream match-up with the great Swiss on Tuesday.

Not that that’s providing any added motivation.

“I don’t think about that because I don’t look at the draw. Now I know,” said de Minaur, whose two hardcourt titles this season are matched only by Kyrgios and reigning US Open champion and world No.1 Novak Djokovic.

The end of Popryrin’s brave run

Boom youngster Alexei Popyrin smashed his racquet in anguish after his gallant US Open run came to a gut-wrenching end at Flushing Meadows.

The Australian was unable to contain his frustrations after failing to serve out a titanic fourth set in a 6-4 6-4 6-7 (3-7) 7-6 (7-2) third-round loss to Italian Matteo Berrettini on Saturday night.

Popyrin was hoping to reach the last 16 at a grand slam for the fourth time and was left shattered at falling short after battling for more than three-and-a-half hours against the 24th seed.

The 20-year-old appeared to lack energy in the opening two sets, Berrettini breaking once in each to assume control.

The Italian also conjured a multitude of break points with Popyrin serving at 2-2 and 4-4 in the third set.

But the Australian held firm and was rewarded for his tenacity by taking the third set.

Re-energised, Popyrin fired up his box, which included Serena Williams’ coach Patrick Mouratoglou and Davis Cup captain Lleyton Hewitt, as the fightback began.

He found another gear in an epic 11th game of the fourth set, forcing Berrettini to stave off six break points.

He couldn’t deny Popyrin on a seventh occasion, the youngster igniting the crowd on showcourt 17 with his adrenaline-charged celebration after rifling a backhand past Berrettini and sprinting all the way to the changeover.

Popyrin, though, may rue popping too early after handing the break straight back before losing the tiebreaker – and the match.

Berrettini will play Russian Andrey Rublev for a place in the quarter-finals.

-AAP