Ana Konjuh’s huge upset at US Open against Agnieszka Radwanska

Despite the power gap, Radwanska held her own in both sets, but the Pole could only manage one break of serve against Konjuh on the night in three opportunities.

It was a David and Goliath clash of physical opposites, but the 6-foot-11 (2.11 m) Karlovic’s tennis game, apart from his prodigious serve, was overshadowed by the skills of Nishikori, more than a foot shorter at 5-10 (1.78 m).

Simona Halep also progressed to the last eight of the year’s final grand slam.

“It’s never easy against someone like Ivo, he has a great serve”, Nishikori said about the Croat, who crushed a US Open record 61 aces in his five-set, first-round win over Lu Yen-Hsun of Taiwan. The second set was almost identical to the first, with Nishikori grabbing a single break of serve in the opening game and dropping just three points on his serve to take a commanding two-set lead.

The 2012 title victor at Flushing Meadows, Andy Murray, eased into the quarter-finals for the 22nd time in his past 23 majors, beating 22nd seed Grigor Dimitrov 6-1, 6-2, 6-2.

“I’ve been playing well, especially today”, the Japanese said.

“I didn’t have any wind or sun or anything that’s going to distract me”, Konjuh said, “so I just played my game and gave my best”. She played in a manner of the experienced player and beat the fourth-seeded Polish Agnieszka Radwanska in straight sets. “So that makes me a little more relaxed”, said Nishikori. I had match points and I missed forehands on all of them. The win marks the biggest of the 18-year-old’s career so far and sends her to her maiden Grand Slam quarterfinal.

Venus – the sixth seed – was unable to add a second Williams name to the quarter-final program following her three-set loss to Karolina Pliskova.

The 18-year-old, who won the 2013 U.S. Open juniors title after claiming the Australian Open juniors crown, lost her first service game but did not yield serve again in an overpowering performance that belied her world ranking of 92.

“I’m still young. I still need to experience things”. She turned her ankle badly but attempted to finish the match to no avail on one good leg.

“I don’t know what would happen if that would be open”.

The hard-hitting Croatian was not intimidated by the bright lights of Arthur Ashe Stadium and played assertive tennis from start to finish.

Radwanska is now 0-5 in fourth-round matches at the U.S. Open, the only Grand Slam event where she hasn’t been to the quarterfinals at least once. ‘This time I got revenge, so I’m really happy.