Heather Watson raced to a 5-2 lead against China’s Zhang Shuai before her opponent was forced to retire with a knee injury on day three of the Viking Classic Birmingham.

The British No.2 was in total control against Zhang – who reached the final of last week’s Viking Open Nottingham – breaking her opponent twice and smashing seven aces as she cruised to a 5-1 lead.

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Watson did have a chance to wrap up the set, playing a sublime drop shot winner to set up a sole set point, but Zhang rallied to hold serve and deny her opponent.

But after stopping for the second time in the match to get medical help for her heavily-strapped knee, the 32-year-old was forced to throw in the towel and hand Watson a spot in the quarter-finals.

“I could tell from the first point she wasn’t at her best,” Watson said. “She had such a great week last week so I’m not too surprised given all the great tennis she’s been playing.

“She is one of the nicest players on tour, nobody has a bad word to say about her, so I hope she recovers quickly in time for Eastbourne or Wimbledon.

“Even though she was hurting I was very happy with how I was striking the ball today, so hopefully I can bring that into my next match.”

Next up for Watson is Croatia’s Donna Vekic, the number three seed, who overcame Italy’s Camila Giorgi in a thrilling three-set contest with a 2-6, 6-3, 6-4 win.

After losing the first set 6-2 Vekic bounced back to claim the second 6-3 and after sailing to a 5-1 lead in the third the World No. 54 let five match points slide by.