Kostyuk had ended the fairytale run of the Russian qualifier in some style, winning 6-2, 6-1. The 20-year-old Timofeeva had accounted for two major scalps, beating former champion Caroline Wozniacki and 10th seed Beatriz Haddad Maia on her Grand Slam main draw debut to reach the second week.
Kostyuk was also in uncharted territory, playing for the first time in the second week at Melbourne Park. But the gulf in experience and ranking was notable, with the World No. 37 breaking Timofeeva four times and protecting her own serve, which was impregnable throughout.
After the match, Kostyuk and Timofeeva did not shake hands, which is now a regular occurrence when tennis players from Ukraine face those from Russia and Belarus. That is because of the current full-scale invasion by Russia in Ukrainian land, in which Belarus is a key ally.
Kostyuk slammed the rival Grand Slam tournament's social media handle, the US Open, which put the Russian flag on the score graphic in front of Timofeeva's name. The post has drifted from the WTA's stance since the war began, where athletes from Russia and Belarus are only allowed to compete as neutral athletes.
An annoyed Kotyuk took to X (formerly Twitter) to share her disapproval of the US Open's post, which deviated from the standard approach and condemned them for promoting "Russian peace," as indicated in her lengthy message.
Kostyuk is a staunch critic of actions from pro-Russian people amid the ongoing war, which began in early 2022. And she has been vocal about the limited support accorded to Ukrainians at the 2024 Australian Open.
Shortly after that incensed reaction, the US Open's Instagram account deleted the post and instead put Kostyuk's photo following her fourth-round victory. The 21-year-old will play fourth seed Coco Gauff in the quarterfinal on Tuesday, in what will be the first of her career.
"Today, after my victory over the athlete from the aggressor country, the Russian flag was published on the official resource of one of the biggest tennis tournaments in the world. The sports world continues to promote a murderous country and a country that uses its athletes as part of its propaganda.
"I call on media representatives, officials and the sports community to stop using the tennis court to promote ‘Russian peace’. We have repeatedly asked the question, ‘What is the status of a neutral athlete?’ Because it actually does not exist."
"These athletes have repeatedly said that everyone knows which countries they represent. Their government constantly says that these are their athletes and the world knows about it. The international media in their publications write that these are Russian and Belarusian athletes. Many athletes have their flag on social networks."