BIRMINGHAM, ENGLAND - JUNE 13: Shuai Zhang of China in action against Sloane Stephens of the USA during Day Five of the Aegon Classic at Edgbaston Priory Club on June 13, 2014 in Birmingham, England. (Photo by Jordan Mansfield/Getty Images for Aegon)

Birmingham, United Kingdom – Zhang Shuai, the hard-working world number 34 from Tianjin, caused a high-speed upset to reach the semi-finals of the lucrative Wimbledon warm-up event, the $700,000 Aegon Classic.

Zhang needed less than an hour to dismiss Sloane Stephens, the third-seeded American 6-3, 6-1, eventually demoralising an opponent who is the second youngest player in the top 20 and has been widely tipped to push on towards the top 10.

The 21-year-old Stephens gradually became prey to disappointment and self-criticism as Zhang's tenacious consistency increasingly lured her opponent into errors and disruptive emotions.

It was an even more surprising success because Zhang, the second highest ranked Chinese player, considers grass her least favourite surface. Now though she has a chance of emulating Li Na, the Chinese number one, who won this title four years ago.

“I think today because I was on centre court I felt great,” said Zhang, her words bringing an approving response. “There were so many people watching and supporting me. I think this is why I played well.

“I said that I would never play well on grass but this is really a good tournament for me. I am still learning every day how to play on grass.”

She was helped in this by her coach Liu Shuo, who applauded Zhang's efforts to be more aggressive even when she once stepped uncertainly into mid-court and slapped a drive volley many feet wide of the court.

Mostly though Zhang created controlled pressure off the ground, served deep and consistently, and took perceptive advantage as Stephens' error ratio surged alarmingly upwards.

Stephens certainly had enough weapons to turn the match round, but after dropping serve early on and trailing 1-4 and 2-5 she was already beginning to fret at her failures.

Her problems were compounded by an unfortunate second game in the second set when first a bad bounce and then a net cord denied her points. From then on it was mostly downhill.

Two double faults cost Stephens another break of serve in the next game, and Zhang was not in the mindset to let such a big lead slip. She rallied tenaciously to cling to her next two service games, and fastened an unbreakable grip on the match.

It earned her a third semi-final of the year. Zhang next plays Ana Ivanovic, the top-seeded former world number one from Serbia, who reached the semi-finals with a 6-1, 6-4 win against Klara Koukalova, the sixth-seeded Czech. – Sapa-AFP