HIGHLIGHTS-Day eight at the U.S. Open

Open tennis championships on Monday (all times GMT):

1938 PLISKOVA KNOCKS OUT SIXTH SEED VENUS WILLIAMS

Women's 10th seed Karolina Pliskova of Czech Republic beat twice former U.S. Open champion Venus Williams 4-6 6-4 7-6(3) in a marathon fourth-round encounter to move into the quarter-finals of the tournament for the first time in her career.

1925 HALEP SAYS SHE IS PLAYING EVER BEST TENNIS

"Well, my game now I feel is the best that I had ever, because I feel strong on my body. I feel that I can control every tactic during the match. I can change. I'm able to the change the tactic when I need," Romanian fifth seed Simona Halep said after beating Spaniard Carla Suarez Navarro 6-2 7-5.

"I feel strong mentally, even if I have some bad moments during the matches."

MARCHENKO FORCES FOURTH SET AGAINST WAWRINKA

Ukraine's Illya Marchenko fought back from a break down to win a tight third set 7-6(5) and force a fourth set against men's third seed Stanislas Wawrinka. The Swiss won the first two sets 6-4 6-1.

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Del Potro into U.S. Open quarters after Thiem retires

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Djokovic shakes rust with romp into quarters

Kerber reaches US Open quarters, closes in on No.1 slot

Countdown on as Pouille's career set to skyrocket

Nadal vows to keep working, resets goals after Open loss

Pouille tops French charge at U.S. Open

Keys locked out of U.S. Open quarters by Wozniacki

Little-known Sevastova back in the big time after retirement

1855 SELF BELIEF KEY FOR DEL POTRO'S SUCCESS

"Well, I was close to (being) retired before my third surgery, but after that I always believe in myself to come back in tennis. When I made the decision to do the surgery, I always believe I will come back, for sure," Argentine wildcard Juan Martin del Potro said after reaching the last eight.

"And after that, everything change to myself, and now I'm here. I'm playing free."

1715 DOMINIC GIVES UPDATE ON HIS INJURY

"It was the knee. So, yeah, I had some problems with blisters, and maybe because of the compensation the knee started to hurt," eighth-seeded Austrian Dominic Thiem said after retiring hurt against del Potro.

"But anyway, I'm going to do an MRI now in the next couple hours, and then I will have more information about it."

1651 HALEP ADVANCES TO QUARTER-FINALS

Women's fifth seed Simona Halep moved into the quarter-finals of the U.S. Open after dispatching 11th seed Carla Suarez Navarro of Spain 6-2 7-5.

1635 INJURY FORCES THIEM TO RETIRE

Wildcard Juan Martin del Potro moved into the quarter-finals of the U.S. Open after men's eighth seed Dominic Thiem was forced to retire due to an apparent knee injury.

The 2009 U.S. open champion was leading 6-3 3-2 when the Austrian retired.

1500 PLAY GETS UNDERWAY ON MAIN SHOWCOURTS

Play gets underway on the main showcourts on a partly cloudy day in Flushing Meadows.

ORDER OF PLAY

ARTHUR ASHE STADIUM (Play starts at 1500 GMT/11 AM ET)

8-Dominic Thiem (Austria) v Juan Martin del Potro (Argentina)

Not before 1630 GMT/12:30 PM ET

10-Karolina Pliskova (Czech Republic) v 6-Venus Williams (U.S.)

1-Serena Williams (U.S.) v Yaroslava Shvedova (Kazakhstan)

Not before 2300 GMT/7 PM ET

22-Grigor Dimitrov (Bulgaria) v 2-Andy Murray (Britain)

4-Agnieszka Radwanska (Poland) v Ana Konjuh (Croatia)

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LOUIS ARMSTRONG STADIUM (Play starts at 1500 GMT/11 AM ET)

11-Carla Suarez Navarro (Spain) v 5-Simona Halep (Romania)

Illya Marchenko (Ukraine) v 3-Stan Wawrinka (Switzerland)

Not before 1900 GMT/3 PM ET

6-Kei Nishikori (Japan) v 21-Ivo Karlovic (Croatia)