Trailing against a woman trying to become the first qualifier in the US Open quarterfinals since 1981, Victoria Azarenka needed every ounce of her experience and skill to advance.

Twice a major champion and twice a runner-up at Flushing Meadows, Azarenka took four of the last five games on Monday night to come back and win 4-6, 6-4, 6-4, ending the surprising, out-of-nowhere run by 145th-ranked Aleksandra Krunic of Serbia.

"Obviously, I didn't have a lot of data on her," the 16th-seeded Azarenka said about her 1.63-meter opponent. "I was a little bit surprised that she's not that tall and she hits the ball and unleashes her forehand with so much power."

The varied game played by Krunic, a 21-year-old from Serbia, worked wonders earlier in the tournament when she used her mix of spins and speeds to eliminate two-time Wimbledon champion Petra Kvitova in the third round and 27th-seeded Madison Keys in the second.

That run of success, which followed three victories in the qualifying rounds, meant Krunic, as she described it, "started maybe loving myself a little bit more".

"Everybody can hit forehand or backhand or serve," Krunic said. "Yeah, it's more about how you get it all together."

By making it to the fourth round, she earned a check for $187,300 - nearly matching her career take coming in. Asked if she knew what her US Open prize money would be, Krunic said: "No. I know it's 30 percent tax. That makes me very sad."

Her ranking would have been the lowest for a quarter-finalist in US Open history, although other women - such as 2009 champion Kim Clijsters - have made it that far without any ranking at all because of a lack of activity.

And the crowd showered Krunic with loud support throughout the match under the lights in Arthur Ashe Stadium, something she said surprised her.

When the match ended, and Azarenka was pulled aside for an on-court interview, Krunic stuck around so the players could walk off together - the sort of thing that rarely happens at the US Open.

Next up for Azarenka is 17th-seeded Ekaterina Makarova of Russia, who advanced earlier on Monday by beating No 7 Eugenie Bouchard 7-6 (2), 6-4.