Belgian Elise Mertens sent American second seed Sofia Kenin out of the US Open with a convincing 6-3 6-3 win to advance to the quarter-finals on Tuesday (NZ time).
Mertens, seeded 16th at Flushing Meadows, played solid from the baseline, kept her errors to a minimum and broke Kenin's serve three times to take out the opening set comfortably.
The frustrations grew for the error-prone Kenin, who committed three unforced errors to be broken at love in the sixth game of the second set and Mertens closed out the match with an ace.
Mertens will meet Victoria Azarenka in the quarter-finals, after the Belarusian rallied from a set down to beat Czech Karolina Muchova 5-7 6-1 6-4 in her fourth-round tie.
The 31-year-old twice Australian Open champion was broken three times in the opening set but 20th seed Muchova looked increasingly hampered by a problem with her upper left thigh on Louis Armstrong Stadium.
Azarenka, on a high after winning her first title for four years at the Western and Southern Open, took full advantage of Muchova's discomfort to whip through the second set and even up the contest.
Muchova took a lengthy medical timeout and returned heavily strapped for the decider but unseeded former world number one Azarenka would not be denied and marched on to a last eight date with Mertens.
Earlier, Serena Williams advanced to the quarter-finals, after a gritty, tension-soaked 6-3 6-7(6) 6-3 win over Greece's Maria Sakkari.
The 23-time Grand Slam winner came up short in the second-set tiebreak, with her power serve abandoning her when she needed it most.
Sakkari carried the momentum into the third set, as she started the decider with a break.
But the 38-year-old American once again showed the battling instincts that has made her one of the all-time greats. She broke back to level for 2-2, as Sakkari's forehand started to misfire.
The six-time Flushing Meadows champion marked her 100th win on Arthur Ashe Stadium with a roar that could be heard all around the grounds.
"I just kept fighting," says Williams, who lost to Sakkari two weeks ago at the Western & Southern Open.
"She was doing so well, she was being so aggressive. I knew I needed to do the same thing."
Williams will play unseeded Tsvetana Pironkova in the quarter-finals on Thursday.
The tearful Bulgarian dedicated her astonishing US Open run to her two-year-old son after she surprised the field by advancing to her first ever quarter-final in New York.
Pironkova's last tournament was at Wimbledon in 2017 and the unranked 32-year-old secured her place in the draw at Flushing Meadows with a protected ranking given to players who take a maternity break.
Unfancied and overlooked, not many expected her to make it to the second week at the start of the tournament but she has come through with notable scalps such as twice Grand Slam champion Garbine Muguruza and 18th seed Donna Vekic.
Pironkova battled through fatigue in a near-three hour contest to beat France's Alize Cornet 6-4 6-7(5) 6-3 in the last-16 and then choked back tears while talking about her son Alexander.
"I haven't seen him in two weeks," she says. "It's very tough, it gets tougher every day. I know he's watching me and I know he's proud of me - and it's worth it."
Pironkova is one of nine mothers in the draw and she admitted that motherhood had changed her not only as a person but also as a tennis player.
"Obviously you become a different person," she added. "You don't focus on yourself that much anymore, like your focus is primary on your child.
"I guess that's a good thing. I'm a lot more organised as well. I have more mental endurance also. Physically I know my body better."
Pironkova will count on all that mental strength when she takes on the most formidable mum in the last eight - Williams - who she has not beaten in four attempts.
"She's a great champion and it's always an honour to play against her," Pironkova said.
"She's obviously a legend. Physically... mentally she's super strong, she has it all."
Reuters
