U.S. Open 2015: Jack Sock collapses in heat

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Overland Park native Jack Sock collapsed in the heat Thursday during the U.S. Open.

(CNN) — The oppressive heat and humidity at the U.S. Open continued to take their toll as Jack Sock, an American seeded 28th, collapsed to the court and retired against Ruben Bemelmans.

After hitting a serve at 1-2 in the fourth set, Sock clutched his left leg. He was unable to move and seconds later fell backward toward the court and had to be assisted by an ATP trainer.

A faint-looking Sock, who won the Wimbledon doubles title in 2014 alongside Vasek Pospisil, was helped off the Grandstand and the 107th-ranked Bemelmans reached the third round at a grand slam for the first time despite trailing two sets to one.

Sock became the 13th retirement at this year’s tournament after a record 12 called it quits in the first round, the heat a major contributor. Temperatures have soared to 30 degrees Celsius — at least — the first four days with only mild respite forecast for the ensuing days.

Sock retired, too, last year at the U.S. Open with a calf injury.

Azarenka Serena’s main threat?

What do Victoria Azarenka, Simona Halep, Garbine Muguruza, Samantha Stosur and Angelique Kerber have in common? They’ve all beaten Serena Williams.

Williams, if only slightly, must have been relieved then to see the quintet land in the opposite half of the draw at the U.S. Open as she chases an achievement — winning all four majors in one season — that might surpass her countless others.

All five had plenty of work to do to set up a potential clash with the world No. 1 in the final and one of them, Muguruza, certainly won’t be looking ahead. The ninth seed from Spain was upset Thursday by qualifier Johanna Konta in three hours, 23 minutes — the longest women’s singles match in tournament history.

Of the remaining four, Azarenka might be Williams’ main threat.

The former No. 1, who defeated 2009 U.S. Open semifinalist Yanina Wickmayer 7-5 6-4 in the second round, held three match points against Williams in Madrid in May. She led Williams by a set and break at the French Open weeks later and at Wimbledon, took the opening set in a quarterfinal that was regarded by many as the highest-quality women’s encounter of the fortnight.

And both times Williams and Azarenka — seeded 20th after a foot injury last year sent her ranking tumbling — met in the U.S. Open final, it went the distance.

Thus Williams won’t need to be told of the danger the Belorussian poses.

But for now Azarenka’s focus is on Kerber, who made her breakthrough by reaching the last four in New York in 2011. The 11th seed ousted Karin Knapp 7-5 6-2.

Muguruza has endured a miserable spell since falling to Williams in the Wimbledon final, going 1-3 and severing ties with longtime coach Alejo Mancisidor last week.

It was the perfect time to pounce for Britain’s Konta, who extended her winning streak to 15 matches at all levels with the 7-6 (4) 6-7 (4) 6-2 victory.

Halep, a loser to Williams in a final in Cincinnati last month, earned another confidence boosting win in beating Kateryna Bondarenko 6-3 6-4. Even though the world No. 2 was fully expected to get past one of the mom’s on the women’s tour, Halep failed to eclipse the second round in her previous two majors.

Stosur, the last player to beat Williams in a grand slam final, in 2011 at the U.S. Open, didn’t linger in the steamy conditions as she crushed Evgeniya Rodina 6-1 6-1 in 51 minutes.

The Aussie, though, wasn’t entirely content. Stosur took aim at organizers, claiming she couldn’t get a car to the venue this week and that Williams kicked her off a practice court.

“I’m not trying to make a big deal about it,” the normally mild mannered Stosur was quoted as saying by AAP. “It’s not just my situation. There are many players in the same boat.

“I think they are always trying to improve and other parts of the tournament are fantastic.

“I understand it’s not easy to take care of so many people all the time but to run a tournament I’d be happy with good practice, transport, and laundry.”