The hard-hitting Kazakh, who claimed her second Grand Slam title at the Australian Open in January, fell to Starodubtseva in the second round at Roland Garros, a defeat that may have been on her mind as she struggled to find her rhythm in the opening set.

Starodubtseva took full advantage of Rybakina's struggles with her forehand and broke for a 5-4 lead.

But Rybakina steadied, breaking back with an angled drop shot to level the set.

She saved a set point in the tiebreaker with one of her 12 aces, and with the first set in hand, attacked in the second with confidence.

A double fault from Starodubtseva handed Rybakina a break to open the second, and Rybakina maintained the edge to finish the job in just under two hours.

"It was a tough match," Rybakina said. "I feel like it wasn't my best performance, but Yuliia, she's a great player. Last time we had a battle, too, and I'm glad I could win in straight sets."

Rybakina now just needs two wins - to reach the semi-finals - to be assured of supplanting Aryna Sabalenka atop the world rankings - even if Sabalenka wins a third straight US Open title.

"Not there yet," she said. "It's still very far. I need to focus on my next match and not think about it."

That next match will be against four-time Grand Slam champion Naomi Osaka, who beat Elise Mertens of Belgium 6-3, 3-6, 7-5.