Aryna Sabalenka defeated Cristina Busca 6-1, 6-4 to srorm into quarters
Sabalenka will face Marketa Vondrousova in the last eight
Vondrousova caused an upset beating ninth-seed Elena Rybakina 6-4 5-7 6-2.
Aryna Sabalenka cruised into the quarter-finals of the US Open after a straight-sets win over Cristina Busca.
The world number one did not face a single break point in her 6-1 6-4 victory over Busca, which lasted an hour and 13 minutes.
Sabalenka, who is aiming to become the first player since Serena Williams in 2014 to retain the US Open title, will face Marketa Vondrousova in the last eight.
Vondrousova caused an upset in New York after overcoming ninth-seed Elena Rybakina 6-4 5-7 6-2.
Sabalenka has won five of their eight meetings against 2023 Wimbledon champion Vondrousova, including a 7-5 6-1 victory at the Cincinnati Open at the start of August.
“I'm not playing not to lose, I play to win," Sabalenka said when asked about her title defence.
“I don't care about what happened last year. I mean, of course it's a big achievement, and I'm super happy I was able to achieve it once, but the goal is to do it many more times.”
Data Debrief: Familiar territory for Sabalenka
Aryna Sabalenka is now the fourth player since 2000 to reach all four women's singles quarter-finals at grand slams in a season as world number one, and the first since Williams in 2016.
The Belarusian is also the first player to reach the women's singles quarter-finals at both the Australian Open and US Open in three consecutive years since Victoria Azarenka (2012-14).
Following her wins over Rybakina and Jasmine Paolini, Vondrousova is the first unseeded player to claim multiple WTA top 10 wins en route to a grand slam quarter-final since Garbine Muguruza, who went on to reach the final at the Australian Open in 2020.
