Two former US Open champions squared off in the third round of the US Open on Louis Armstrong Stadium on Friday, and it was 2016 titlist Angelique Kerber of Germany who overcame 2017 champion Sloane Stephens of the United States 5-7, 6-2, 6-3.

In just under two hours, the No.16 seed Kerber fought back from a set down to eliminate the American. Former World No.1 Kerber also fought back from a deficit in their head-to-head. This is only the second time she has defeated Stephens in seven career meetings.

Stat box: Kerber has now won 17 of her past 19 matches as the three-time Grand Slam champion experiences a resurgent summer. She won her first title in three years on home soil in Bad Homburg, then raced to the Wimbledon semifinals before falling to eventual champion Ashleigh Barty.

It was Kerber who took more advantage of opportunities as the match lengthened, finishing up the clash with four breaks of service out of her nine break points. Former World No.3 Stephens could only muster a 2-for-5 rate on her own break points.

In the first set, Stephens played the cleaner match, with an even number of winners to unforced errors (14 apiece) while Kerber's 18 miscues doubled her winner count during the opening frame. But by the end, it was Kerber who was pristine, with only six unforced errors in the final set compared to Stephens's 15.

Crucial stages: Stephens served for the first set at 5-3, but double faulted on her first set point before dropping serve. Still, the American’s forehand was clicking in the opener, and she broke Kerber at 6-5 to eke out the one-set lead.

However, the second set went the way of Kerber, edging ahead for the first time in that stanza by mixing big hitting from her lefty forehand with devilish dropshots to break for 3-2. All told, Kerber won the last five games of the second set.

That led to a mesmerizing final set, where the rallies became increasingly grueling as both speedy players with excellent groundstroke timing jousted for every point. At 3-2, Stephens had three break points, but she was outrun by Kerber as the German held on for 3-3.

Kerber was rewarded for those efforts, as she converted her fourth break point of the protracted next game after a Stephens volley flew long. Now up a break at 4-3, Kerber chased down every ball as she knocked off rally after rally, and the German broke Stephens once more at 5-3 to clinch a closely-contested decider.

Comments from Kerber: "Playing against Sloane, it's always a tough battle," Kerber told the press, after her win. "I lost the last few matches against her, so I was ready to have a really tough fight. After the first set where she played really well, especially in important moments, I was just trying to stay in the match, being ready for every single ball.

"The third set, I think at the end, two, three points decided the match. I was just focusing for every single ball and taking my chances, being ready, being aggressive. I'm happy that I'm through and being in the second week now."

Next up: Kerber will face Canadian teen Leylah Fernandez in the fourth round, after Fernandez upset defending champion Naomi Osaka on Friday night.

Muguruza - 2021 US Open 3R

Garrett Ellwood/USTA

Muguruza stops last year's finalist Azarenka in three-set tussle

In a hard-fought battle between two-time Grand Slam champions and former World No.1 players, it was No.9 seed Garbiñe Muguruza of Spain who emerged the victor over No.18 seed Victoria Azarenka of Belarus, 6-4, 3-6, 6-2, in the third round of the US Open on Friday.

On Arthur Ashe Stadium, the pair of WTA stars tussled for two hours and 14 minutes before Muguruza ended the run of last year's US Open finalist Azarenka, edging ahead in their career head-to-head by three wins to two.

Stat corner: Muguruza, who has won 2016 Roland Garros and 2017 Wimbledon and was a finalist at the 2020 Australian Open, has never reached the US Open quarterfinals. This marks only her second trip into the round of 16 in New York (also in 2017).

But Muguruza came out on top on Friday by out-winnering Azarenka 34 to 23, and she also had five fewer unforced errors than the Belarusian. Three-time US Open runner-up Azarenka (2012, 2013, and 2020) had six double faults (to Muguruza's four) including the most untimely one: on match point.

Key moments: Muguruza fell behind an early break in the first set but quickly righted the ship to get back on serve. With Azarenka ahead 4-3, Muguruza used exceptional hitting to go on a tear, winning 11 straight points to reach triple set point. She took the one-set lead with an ace.

But Azarenka was unbothered and gritted through stunning rallies to sweep to a 4-0 lead in the second set. At 5-2, two dropshot winners helped her reach triple set point, and she converted the third of those chances with an error-forcing forehand.

Muguruza, though, grabbed the momentum in the decider, after saving two break points at 1-1 with stunning backhands. The Spaniard's depth and power increased while drawing errors from Azarenka, and she won the final four games of the match to triumph.

Muguruza's comments: After the match, the Spaniard said she was "happy because it was a very tough match. I was facing Victoria, she's had so much success in this tournament. I feel like she was comfortable in this court, in these conditions. I was very pumped for the match.

"I started very well, got that first set. Then I feel like in the second set, lost my momentum a little bit. She also came up with great shots. In the third set I managed just to be there again and go for the match a little bit. When you face these types of opponents you cannot wait, you have to go to get the win. I felt I did it."

Next up: Muguruza will have a rematch against No.8 seed and reigning Roland Garros champion Barbora Krejcikova of the Czech Republic in the fourth round, after Krejcikova defeated Russian lucky loser Kamilla Rakhimova on Friday.

Their first two meetings have taken place this season, with Muguruza defeating Krejcikova in the Dubai final, and Krejcikova leveling their rivalry last month in the round of 16 in Cincinnati.

Svitolina wins 8th straight match, sweeps past Kasatkina into fourth round

No.5 seed Elina Svitolina of Ukraine charged into the US Open round of 16 for the fourth time in her last four appearances at the event, ousting No.25 seed Daria Kasatkina of Russia, 6-4, 6-2, in an hour and 14 minutes on the Grandstand court.

With the victory, World No.5 Svitolina extended her current winning streak to eight straight matches. Svitolina won her first title of the season last week in Chicago.

"I knew that I had to be really quick with my mind just to go straight into Grand Slam [after Chicago], try to bring the same intensity, same tennis," Svitolina told the press. "I was playing quite good my first round, then second round, and today was even better I would say with my tennis. I'm happy where I am right now."

2019 US Open semifinalist Svitolina continued her mastery over Kasatkina: the Ukrainian is now 6-0 over the Russian. In the first meeting between the two in over two years, Svitolina saved all three break points she faced as she advanced.

Kasatkina did finish the match with one more winner than Svitolina (26 to 25), but Svitolina kept her unforced error count much lower, with just 14 compared to 22 by Kasatkina. 

After missing her first four break chances, Svitolina at last broke the Kasatkina serve at 4-4 by forcing an error wide. Svitolina then stared down a break point in the next game while serving for the set, but she erased it with a strong serve before wrapping up the set with a winning putaway.

Svitolina methodically moved through the second set after breaking Kasatkina in the first game, steering to victory and setting up an intriguing round-of-16 clash with former World No.1 Simona Halep of Romania.