Rafael Nadal sparked his China Open campaign into life as he stormed into the quarter-finals with a much-improved 7-6 (7/3), 6-4 victory over Canada’s Vasek Pospisil on Wednesday.

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The 14-time Grand Slam winner had his service broken four times in the first round by China’s 230thranked Wu Di, but he showed better signs against Pospisil, the world No44.

Spain’s Nadal, groping for form after a difficult year, will now face America’s Jack Sock in the last eight as he looks for a confidence-boosting fourth title of the season.

Nadal also avoided joining Tomas Berdych on the sidelines after the Czech, who won the rain-delayed Shenzhen Open on Monday, became the latest big name to fall in Beijing.

“Every improvement is important,” said Nadal. “Obviously I improved from yesterday. I played a much better match than yesterday. Every victory gives me opportunities to keep practising the things that I need to practice. 

“Practising outside of the competition is very important, but at the end you have to compete well. Every match is an opportunity for me.”

Earlier, and in much smoggier conditions, Berdych and Caroline Wozniacki both lost their way at a tournament which is proving a graveyard for senior players.

Second seed Berdych never hit his stride against Uruguay’s 37th-ranked Pablo Cuevas as he was dumped out 6-4, 6-4 to become the tournament’s latest upset.

“I made one tournament title. The other one didn’t go my way,” shrugged the Czech.

Later former world No 1 Wozniacki was brutally disposed of by Angelique Kerber 6-2, 6-3 in a defeat which ended her hopes of reaching the year-ending WTA Finals.

“I’m going home. I’m trying to catch a flight that is in a couple of hours,” said Wozniacki, who was in no mood to hang around after her defeat.

Andrea Petkovic was also bundled out by Sara Errani 3-6, 6-3, 6-2, compounding a tough season which has included food poisoning, injury and a first-round defeat last week in Wuhan.

It was a different story for Garbine Muguruza, who retired from last week’s Wuhan final against Venus Williams with an ankle problem but bounced back to beat Irina Falconi 6-2, 6-1. The Spaniard will now qualify for the WTA Finals if she wins her next match against Mirjana Lucic-Baroni. 

Fourth seed Agnieszka Radwanska set up a quarter-final with Kerber after Madison Keys retired after their first set.