Novak Djokovic contests his 100th Wimbledon match on Sunday as he continues his push for a record-equalling eighth title while Iga Swiatek aims to make the quarter-finals for the first time.
Djokovic tackles Poland's Hubert Hurkacz on Centre Court, where he has not lost in 10 years.
However, if he is to continue his bid for a third major of 2023, and match Margaret Court's all-time record of 24 Slams, he needs to find a way of battering through the seemingly impregnable Hurkacz defence.
The Pole has not dropped serve at the tournament, saving all 11 break points he has faced and winning all 46 service games.
"I don't see too many holes in his game," said Djokovic who has a 5-0 record against the 18th-ranked Hurkacz, including at Wimbledon in 2019.
"He serves extremely powerful, covers the court very well. He has very long arms and a very good feeling at the net."
Hurkacz made the semi-finals in 2021, having become the last man to defeat Roger Federer at Wimbledon in the quarter-finals.
Twelve months ago, however, he crashed out in the first round.
After being banned from Wimbledon in 2022 over the war in Ukraine, seven players from Russia and Belarus have made it to the last 16 in men's and women's singles.
Russian seventh seed Andrey Rublev kicks off the action on Centre Court, hoping to complete a full set of quarter-finals at all four Slams.
The 25-year-old faces Alexander Bublik, born in Russia but representing Kazakhstan.
Bublik, the world number 26, defeated Rublev on grass in the Halle final in June.
Another Russian, Roman Safiullin, has made the last 16 on his main draw debut.
The world number 92, who had never previously got beyond the second round of a Slam, faces 2021 semi-finalist Denis Shapovalov.
- Ukraine v Belarus -
Jannik Sinner, the eighth-ranked Italian, takes on unseeded Daniel Elahi Galan of Colombia, hoping to secure a second successive quarter-final.
Women's world number one Swiatek, the reigning US Open and French Open champion, has not dropped a set yet on her way to the fourth round for a second time.
She takes on Swiss 14th seed Belinda Bencic, who had fallen in the first round in her past two visits.
In a last-16 clash tinged with political significance, Victoria Azarenka of Belarus takes on Ukraine's Elina Svitolina.
At the French Open, Svitolina and all Ukraine players refused to shake hands with opponents from Russia and Belarus.
"I won't sell my country out for likes," said Svitolina after refusing to shake hands with world number two Aryna Sabalenka of Belarus in Paris.
Svitolina was even booed by the French crowd for her defiant stance.
At last year's US Open, Ukraine's Marta Kostyuk offered only a tap of the racquets after facing Azarenka.
Both Svitolina and Azarenka are former semi-finalists at the tournament. Azarenka, however, enjoys a 5-0 head-to-head record over the Ukraine player.
A second Ukrainian, Lesia Tsurenko, faces world number four Jessica Pegula, with both women seeking spots in the last eight for the first time.
The 34-year-old Tsurenko reached the fourth round after triumphing in the longest-ever tiebreak in a Grand Slam women's singles match -- 38 points -- against Romania's Ana Bogdan on Friday.
Tsurenko took victory on a seventh match point after saving five match points herself in a three-hour 40-minute epic.
Sunday's other last-16 tie is an-all Czech clash between Marie Bouzkova, who put out fifth seed Caroline Garcia in the third round, and Marketa Vondrousova, the 2019 French Open runner-up
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