MELBOURNE, Australia -- Dayana Yastremska and Linda Noskova reached their first Grand Slam singles quarterfinals in contrasting fashion on Monday at the Australian Open.

Yastremska beat two-time champion Victoria Azarenka 7-6 (6), 6-4 while 18th-ranked Elina Svitolina was trailing Noskova 3-0 when Svitolina retired with a back injury.

Azarenka served for the first set twice and had two set points at 6-5 but couldn't take them and Yastremska won the opening set on her second chance after 74 minutes. The Ukrainian then led 3-0 in the second set but Yastremska won six of the next seven games to clinch victory, ending with 37 winners.

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"I think I need to take a thousand breaths because my heart I think is going to jump out of my body," Yastremska said.

"During the match, I was imagining how I lost already like 25 times. I was losing the tiebreak, second set I was losing, I always felt I was running behind the train. But because I'm a little bit of a fighter I think I won this match and plus the support, it was amazing."

There was no handshake, as is the convention between Ukrainian and Russian and Belarusian players, though Yastremska raised her racket toward Azarenka.

The first game of the Noskova-Svitolina match lasted 11 minutes and contained 20 points. Noskova broke serve and held for 2-0 before Svitolina had a timeout and received treatment on her lower back.

When she resumed, the Ukrainian's serve speed was well down and her movement appeared compromised. After being broken for a second time and fighting back tears, Svitolina shook Noskova's hand and retired.

Svitolina said the injury happened at the end of the first game.

"I got a spasm, like a shooting pain," she said. "Couldn't do anything, completely locked my back, just very sad. I had some injuries to my back before where it just was tiredness the next day of the match, but this one was really out of nowhere. I felt like someone shot me in the back."

Noskova beat top-ranked Iga Swiatek in the third round.

"Obviously today was not the way I had planned to win," she said. "I feel (sorry) for Elina, I hope she gets very well soon."