No.7 seed Iga Swiatek of Poland got through another three-set tussle this week, as she outlasted No.28 seed Anett Kontaveit of Estonia, 6-3, 4-6, 6-3, to reach the round of 16 at the US Open for the first time in her career.

2020 Roland Garros champion Swiatek, who came back from 3-6, 6-6 down to scrape past Fiona Ferro in the previous round, needed a challenging two hours and 17 minutes to overcome surging Kontaveit, who won her second career WTA singles title just last week in Cleveland.

Stat box: Kontaveit had won their first two meetings, including a grueling, two-and-three-quarter-hour battle in the fourth round of the Australian Open last year. But Swiatek beat Kontaveit during her attempted title defense at Roland Garros earlier this season, and she made it two in a row on the Grandstand court in New York, leveling their head-to-head.

Swiatek is the first Polish woman to reach the round of 16 at the US Open since Agnieszka Radwanska did so in 2016. But it was a tough test getting past Kontaveit, as the Estonian fended off 14 of Swiatek's 19 break points in total. Still, Swiatek dropped serve one fewer time than Kontaveit in the clash.

In the closely-contested hard-hitting tilt, Kontaveit had five more winners than Swiatek (37 to 32), but also seven more unforced errors than the Pole (34 to 27).

Swiatek has now made the second week of all four majors this year -- the only WTA player to accomplish that feat in 2021.

How it happened: Swiatek took charge of the opener by breaking an error-prone Kontaveit for 5-3, then held on for the one-set lead. But in the second set, Kontaveit (who had twice been up a break) gritted out a tough hold for 5-4, then drew double faults and miscues from Swiatek to break in the next game and tie the match.

The stage was set for a thunderous third set as the groundstroke velocity ramped up. At 1-1, Kontaveit seemed to be cruising to a hold up 40-0, but Swiatek used heavy hitting to set up an error-forcing backhand and reach break point, which she converted to lead 2-1.

Swiatek had two chances to go up a double-break at 3-1, but Kontaveit got through that game, closing with a backhand winner. Nevertheless, Swiatek got more opportunities on the Kontaveit serve when she held five match points at 5-3. The first four were saved by the Estonian with two big backhands and two aces, but on the fifth, Kontaveit sent a forehand long.

Iga says: "That's my first time in the fourth round of US Open, I'm pretty proud of that," the Pole said, after her win. "We did a great job. Being in fourth round of all the Grand Slams this year, it shows that really I am going the right path.

"The match was exciting, was kind of stressful, really physical, because we had games when we had so many ad [points], so long, that I could feel that I'm getting more and more tired. But I knew that I'm well-prepared. I'm pretty happy actually I could for the first time show the tennis that I was playing on practices, that I was working on."

"I'm trying to solve problems," Swiatek added. "Sometimes like during a match against Fiona Ferro, when all the emotions come in, it's pretty hard to see everything clearly. I'm glad that today I was in a different mindset and my head was more clear because I could actually solve problems. I think that was the reason I won that match."

Next up: In the fourth round, Swiatek will meet No.11 seed and Olympic gold medalist Belinda Bencic, who defeated 23rd-seeded Jessica Pegula in straight sets earlier on Saturday. In their only prior meeting, Swiatek dispatched Bencic in this year's Adelaide final, 6-2, 6-2.

Sakkari stumps Kvitova in US Open third-round clash

No.17 seed Maria Sakkari of Greece moved into the US Open round of 16 for the second year in a row by dispatching No.10 seed Petra Kvitova of the Czech Republic, 6-4, 6-3, on Arthur Ashe Stadium on Saturday afternoon.

Sakkari notched her eighth win over a Top 20 player this season as she swept to victory in an hour and 20 minutes. With the win, Sakkari leveled her head-to-head with Kvitova at 3-3, having lost her two most recent meetings with the former World No.2.

Stat corner: At the start of Saturday, two-time Wimbledon champion Kvitova had won more matches at Grand Slam events than any other player still remaining in the draw (31 major match-wins in her career).

But that level of experience was not enough against the rising Sakkari, who posted her best Grand Slam result earlier this season when she reached the Roland Garros semifinals. Sakkari had 19 winners to 16 unforced errors in the match, and saved the two break points she faced on the day.

By contrast, Kvitova's powerful left-handed game was off-form, as her 16 winners were more than doubled by 33 unforced errors. The big-serving Czech was even out-aced by Sakkari, by nine to five.

Key moments: Kvitova had the first big opportunity of the match when a stellar forehand down the line gave her double break point at 2-1. But the Czech missed three consecutive returns from there to give Sakkari game point, which the 17th seed converted to hold on for 2-2.

That began a crucial swing, as a powerful return by Sakkari in the very next game gave the Greek the lone break of the set for a 3-2 lead. Sakkari expertly held on from there, serving out the set at love with sturdy strikes which were unsuccessfully returned by Kvitova.

Sakkari broke serve in the first game of the second set and she rolled to victory from there, collecting a second and final break of the set in the last game of the match for good measure.

Words from the players: "I think it was a great match," Sakkari said afterwards. "It's always tough to play against Petra, because she hits very hard, probably the hardest on the tour. She's lefty, so it makes your life even tougher. I was prepared that I'm gonna have to hit out of her rockets, but I'm very pleased with the way I served, the way I returned, and my attitude on court once again."

And Kvitova praised Sakkari: "I think that she definitely played better than me today. There is no doubt about it. She deserved to win. She didn't really miss anything. I tried, but she really served very well. She didn't really give me the chances. Maybe in the first set I did have two chances, but it was really tough to make them."

Next up: An eye-catching tilt awaits Sakkari in the star-studded round of 16: she will face No.6 seed and 2019 US Open champion Bianca Andreescu, after the Canadian dismissed lucky loser Greet Minnen of Belgium on Saturday.

Pliskova eases past Tomljanovic

No.4 seed Karolina Pliskova of the Czech Republic stormed into the round of 16 at the US Open, cruising past Ajla Tomljanovic of Australia, 6-3, 6-2 in an hour and 11 minutes on the Grandstand court.

"I was just feeling confident coming to this match," Pliskova said, after her win. "Of course, I was serving pretty well, even better than the match before. So that kind of helped me a bit. Even the game from the baseline, I thought it was pretty solid today."

After barely getting past Amanda Anisimova in a high-octane second-round clash, this year's Wimbledon runner-up Pliskova had much less trouble in her following match. She slammed 20 aces and saved all five of the break points she faced in another display of serving mastery.

That made it two straight matches where Pliskova hit 20 or more aces (she hit 24 against Anisimova, setting the US Open record for a women's match since the stat was recorded in 1998).

Pliskova now has six career matches where she has hit 20 or more aces (she has won all six of those matches) and this is the first time two of those matches have come at the same event.

Additionally, this is only the sixth time since 2008 that a player has hit at least 20 aces in a straight-set win. Pliskova has two of those instances, with the other players being Serena Williams (twice), Maria Sharapova, and Sabine Lisicki.

Those service rockets were the majority of the 33 winners the Czech fired in Saturday's clash, outpacing her 24 unforced errors. World No.46 Tomljanovic, who reached her first Grand Slam quarterfinal at Wimbledon earlier this year, had eight winners and 15 unforced errors.

Pliskova was in danger on serve at 1-1, but swatted away two break points to grit out the hold, and then broke Tomljanovic to lead 3-1. Pliskova then faced three more break points at 4-2, but saved each of the trio with a service winner to survive another close call and edge to 5-2.

Two more aces helped her reach set point at 5-3, where she notched the one-set lead with a winning volley. After getting the opening frame in her pocket, Pliskova was far less troubled in the second set, never facing a break point in that stanza as she rolled to the win.

Former World No.1 Pliskova is now into the US Open fourth round for the fifth time in her career. Her best result in New York is a runner-up showing in 2016, when she defeated Serena Williams in the semifinals before losing to Angelique Kerber in a three-set final.