Two-time champion Naomi Osaka suffered a stunning defeat in the third round of the U.S. Open on Friday to Canadian Leylah Fernandez 5-7, 7-6(2), 6-4, ending her title defence inside Arthur Ashe Stadium.

After both players held their serves through the first 10 games, the four-time Grand Slam winner broke Fernandez's serve and then closed out the set in the next game with an ace to cheers from the New York crowd.

But the night quickly turned sour for the third seed as she dropped her serve to send the second set into the tiebreak, where she uncharacteristically lost her cool, whacking her racquet and then flinging it onto the court twice in frustration as Fernandez scored five straight points.

Osaka did not receive a warning or a code violation. Her troubles, though, continued as Fernandez broke her serve to kick off the third set, and she hit a ball into the stands in the second game, prompting a warning.

In the ninth game, Osaka rushed through her serves, not even waiting for the crowd to quiet down, as she was unable to create a single break point opportunity in the final set.

Earlier on Friday on the men's side, Russian Daniil Medvedev ripped through third-round opponent Pablo Andujar 6-0, 6-4, 6-3, his third win in under two hours at this year's U.S. Open.

The world number two held the unseeded Spaniard to five points in the first set, putting up just three unforced errors in a stretch of superb play in his bid for a maiden major title two years after he lost in the final to Rafa Nadal.

The Russian has yet to drop a set at Flushing Meadows this year and showed scarce few moments of vulnerability on Friday. He recovered from a double fault in the 10th game of the second set with a pair of aces and fired off 34 winners to Andujar's 16 across the entire match.

Andujar converted one of four break point opportunities late in the third set to wild applause from the fans inside Louis Armstrong Stadium. However, it was two little too late as the Australian Open finalist fired back with a break of his own to clinch the match.

"The main positive is to win in three sets because Pablo was fighting good," said Medvedev, who clinched his fourth Masters 1000 title last month in Toronto. "I was playing good and (I'm) really happy with my level."

He faces a potential challenge in the fourth round from 24th-seeded Briton Dan Evans, who beat world number one Novak Djokovic in Monte Carlo in April and whom Medvedev described as "very smart".

"He doesn't have one shot that is a weapon, and yet he's a top player for many years already," Medvedev told reporters. "The way he chooses the right moment to go to the net, to slice, to make a dropshot. I mean, his serve is not huge, but it's tough to return. Great player."