Second seed Khachanov falls at first hurdle in Hong Kong

Second seed and world number 15 Khachanov, who reached the semi-finals of the Australian Open a year ago, was rocked in his build-up for this year's first Grand Slam of the year by a second-round 7-6 (7/2), 2-6, 6-2 defeat to Finland's Emil Ruusuvuori.

Russia's Khachanov, who had a bye into the second round, struggled for consistency and only found his range when he rattled off four games in a row to take the second set.

But Ruusuvuori, who came from a set down to beat France's Benjamin Bonzi in the first round, regrouped and was always in control in the decider as he broke twice to run out the winner in 2hr 23min.

"It was a very difficult match against a great opponent," said the Finnish world number 69 who will face either Lorenzo Musetti of Italy or Russia's Pavel Kotov on Friday for a place in the semi-finals.

"I've lost a couple of times against him and he's always a very difficult guy to beat."

Third seed Frances Tiafoe had no such problems as he enjoyed comfortable win against Serbia's Miomir Kecmanovic 6-3, 7-6 (7/4).

American third seed Tiafoe, a US Open semi-finalist in 2022, needed just 92 minutes to book his place in the last eight.

"For a first match I thought I played very well," said world number 16 Tiafoe, who had also enjoyed a first-round bye.

"I just wish the second set had been as easy as the first."

Tiafoe will now face rising Chinese teenager Shang Juncheng, who recorded his second big upset win of the week to reach the quarter-finals.

The 18-year-old world number 183, who likes to be called "Jerry", outlasted the Dutch world number 50 Botic van de Zandschulp 6-7 (5/7), 7-6 (7/2), 7-6 (7/2) in a three-and-a-half hour battle of attritional tennis.

Shang will be looking for a third giant-killing of the week against Tiafoe after also coming from a set down to knock out seventh seed and world number 33 Laslo Djere of Serbia in the first round.

"It was a rollercoaster match," said Shang of his win over Van de Zandschulp.

"Three hours 30 on court, but I was feeling very fit so I have a great team and the pre-season with them was amazing."

World number five and top seed Andrey Rublev of Russia will open his 2024 campaign on Thursday with a second-round clash against Britain's Liam Broady.