US Open 2023
Venue: Flushing Meadows, New York Dates: 28 August-10 September
Coverage: Daily live text and radio commentaries across the BBC Sport website, app, BBC Radio 5 Live and 5 Sports Extra
Daniil Medvedev and Andrey Rublev consider each other "family" but they will go head-to-head for a place in the US Open semi-finals on Wednesday.
The two are childhood friends, with Russian third seed Medvedev asking compatriot Rublev, ranked eighth, to be godfather to his daughter.
"I think we have a great relationship," 2021 champion Medvedev said.
"Even if on the court we're big competitors, nothing will come between us to separate us in real life."
The two will play their quarter-final not before 18:30 BST on Wednesday at Arthur Ashe Stadium.
Medvedev reached the final in New York in 2019 and lifted the trophy two years later, while Rublev is still bidding for a first major semi-final.
"I think [the relationship with Medvedev] is something already like family because I'm godfather of his daughter," Rublev said.
"Obviously we built our relationship because of tennis, but now it's already bigger than tennis. We have known each other since we were six.
"He's super honest, super relaxed. It's super easy to communicate with him. At the same time he's really, really funny. When you spend time with him, you always have fun."
Defending champion Carlos Alcaraz faces German 12th seed Alexander Zverev in the final match of the day.
The Spaniard, 20, has dropped just one set in his four matches, while Zverev declared he was back to his best after coming through a tough fourth round encounter with Italian sixth seed Jannik Sinner.
A tantalising rematch of this year's Wimbledon final between Alcaraz and Djokovic remains a real possibility after the Serb beat American Taylor Fritz on Tuesday to reach the last four.
That match was played on the hottest day of the tournament so far during a heatwave in New York, with temperatures expected to rise to 35C on Wednesday.
Sabalenka returns as world number one in waiting
In the women's quarter-finals, Belarusian Aryna Sabalenka continues her bid for a second major title of the year.
Iga Swiatek's last-16 loss to Jelena Ostapenko on Sunday means Sabalenka is guaranteed to replace her as the top-ranked women's player after the tournament.
The second seed, who won her maiden Slam title at January's Australian Open, plays China's 23rd seed Zheng Qinwen from 17:00.
But the 25-year-old said she would have preferred to "battle" Swiatek in the final for the top ranking.
"I pushed myself so hard to not watch the score, [I told myself] just go to bed. I knew if I saw the result it would be really tough to sleep," Sabalenka said.
"To be honest, I didn't want her to lose. I was sad, but at the same time I have to be happy because it's not like she just fell.
"All year I've been playing well. I put her under pressure. I didn't want to become world number one like this. I want a battle for this."
In the other women's quarter-final, Wimbledon champion Marketa Vondrousova meets American 17th seed Madison Keys.
It is the third time Czech ninth seed Vondrousova has reached a major quarter-final. On the previous two occasions she went on to reach the final at the French Open in 2019, before lifting the trophy at SW19 this year.
Keys, a US Open finalist in 2017, will hope to join compatriot Coco Gauff in the semi-finals at their home major.
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