British number one Johanna Konta was made to work hard before advancing to the Bank of the West Classic semi-finals with a 6-2 4-6 6-3 victory over Saisai Zheng.
Third seed Konta broke Zheng twice in the opening set as she started strongly but the second set was a disjointed affair that saw a total of seven breaks of serve.
Zheng took advantage of four of the eight break points she had and won the last three games of the set to level the match.
Konta broke Zheng early in the third set before Zheng rallied with three straight games, but another break saw the Briton move into a 4-3 lead.
She held serve before breaking Zheng for a third time and then holding to secure victory in just over two hours 20 minutes.
Source: PA
