Djokovic saved three breakpoints in stifling conditions to go 5-4 up but lost the opening set in a tough tiebreak as Opelka cranked up his serve
Defending champion Coco Gauff put on a clinical performance to beat Jasmine Paolini 6-3, 6-2 and eliminate the Italian as she registered her first win at the WTA Finals on Tuesday.
Images from the US Open women's singles final between Belarus's Aryna Sabalenka and Jessica Pegula of the United States, at Flushing Meadows, New York, on Saturday.
Images from the US Open women's singles quarter-finals at Flushing Meadows, New York, on Tuesday.
Images from the US Open women's singles semi-finals at Flushing Meadows on Thursday.
The girl, wearing a matching fuchsia Nike kit and sporting a temporary tiger tattoo on her left forearm, emphatically cheered Aryna Sabalenka on
Aryna Sabalenka's return to top spot in the WTA rankings after leapfrogging Iga Swiatek has set up a thrilling end to the season, with next month's WTA Finals in Saudi Arabia likely to prove decisive in the race to end the year as world number one.
Sabalenka, who was set to face American Emina Bektas, was replaced in the draw by Russian Erika Andreeva, while fellow Belarusian Azarenka's spot was taken up by another lucky loser in Frenchwoman Elsa Jacquemot.
Those deep runs have left her better equipped to handle the pressure at the business-end of the majors.
World number one Iga Swiatek edged Aryna Sabalenka 7-5, 4-6 7,-6(7) in a gripping and gruelling Madrid Open final to win the title for the first time on Saturday in what was a repeat of last year's summit clash at the WTA 1000 claycourt tournament.
Tiger-tattooed Aryna Sabalenka clawed her way back from injury and disappointment to hoist the US Open trophy at last.
Sinner won in Cincinnati this week to claim his fifth title of a breakout season before the revelation that he avoided a ban over two positive tests
Elena Rybakina rallied from a set down to beat Russian fourth seed Ekaterina Alexandrova 3-6, 6-0, 6-2 and win the Ningbo Open title on Sunday, as her late surge to reach next month's WTA Finals gained momentum.
IMAGES from Day 1 of the US Open played Flushing Meadows, New York, United States, on Monday.
Second seed Aryna Sabalenka was sent crashing out of the French Open after a shock 6-7(5) 6-4 6-4 quarter-final loss to Russian teenager Mirra Andreeva
Elena Rybakina qualified for the WTA Finals' last four, beating an error-prone Iga Swiatek 3-6, 6-1, 6-0 on Monday, while Amanda Anisimova beat fellow American Madison Keys 4-6, 6-3, 6-2 in Riyadh.
Images from the US Open women's singles third round matches, at Flushing Meadows, New York, on Friday.
Koltsov's death sent a shockwave through the Miami Open where Sabalenka is scheduled to play her opening match
She beat Jasmine Paolini in the quarter-finals and then made it back-to-back wins over top 10 players as she also defeated compatriot Coco Gauff by 6-1, 6-2 in the semifinals.
French Open champion Coco Gauff captured her third WTA 1000 title and first in Wuhan after rallying from two breaks down in the second set to defeat fellow American Jessica Pegula 6-4, 7-5 in Sunday's final.
Images from the US Open women's singles second round matches, at Flushing Meadows, New York, on Wednesday.
Defending champion Jannik Sinner, who has been recovering from illness, received a more favourable route to the US Open final than Carlos Alcaraz while Aryna Sabalenka will be tested in her bid to retain her title after the draw was made on Thursday.
Renowned for his speed on the ice, Koltsov won the Russian Super League title with Salavat Yulaev in 2008 and more recently returned to the club as an assistant coach.
Coco Gauff beat defending champion Iga Swiatek 6-3 6-4 at the WTA Finals in Riyadh on Tuesday to reach the semi-finals and ensure Aryna Sabalenka would finish the year as world number one.
Jasmine Paolini's exit means only one of the top five women's seeds -- world number one Aryna Sabalenka -- will be in the third round. It is only the second time that this has happened in the professional era after Wimbledon 2018.
Images from Day 8 of the 2024 Australian Open in Melbourne on Sunday.
Coco Gauff overcomes Sabalenka in error-riddled final to win French Open
Aryna Sabalenka beat China's Zheng Qinwen 6-3 6-2 to retain the Australian Open women's singles title on Saturday.
French Open champion Gauff is in line for a clash with fellow American Jessica Pegula.
Gauff upset world number one Sabalenka 6-7(5), 6-2, 6-4 on Saturday to win her second Grand Slam singles title.
The two players merely acknowledged each other with a wave before heading off court.
Former champion Emma Raducanu claimed her first victory at the tournament since lifting the trophy in 2021 by beating Japan's Ena Shibahara in the first round on Sunday.
Factbox on American second seed Coco Gauff, who defeated Belarusian world number one Aryna Sabalenka
Coco Gauff was dumbstruck after beating world number one Aryna Sabalenka in the French Open final on Saturday
Carlos Alcaraz demolished Mattia Bellucci to banish memories of last year's shock early exit at the US Open on Wednesday.
Canadian Open champion Shelton was locked in an entertaining contest with Frenchman Adrian Mannarino in the day's opening match on Louis Armstrong Stadium when his tournament suddenly unravelled.
The International Tennis Federation (ITF) named Novak Djokovic and Aryna Sabalenka as its 'world champions' of 2023 after their performances at this year's Grand Slams.
Aryna Sabalenka took a big step towards retaining her Australian Open crown by beating American fourth seed Coco Gauff
Factbox on Belarus' Aryna Sabalenka, who beat China's Zheng Qinwen in the Australian Open final on Saturday
Iga Swiatek arrives at the US Open with her sights set on a seventh Grand Slam title and a potential return to World No. 1 to cap what she calls a remarkable year of redemption following "the worst experience of my life".