Williams rolls on at Taiwan Open, Doi benefits from walkover

Williams was tested early but the top seed was a class above as she won 7-5 6-2 in the quarter-finals.

The seven-time grand-slam winner - looking to claim her first WTA title since November - only served at 47 per cent but still did enough to advance after a little over an hour on court.

Awaiting Williams in the final four is third seed Yulia Putintseva.

Putintseva had just won the opening set 6-3 when Swiss opponent Stefanie Voegele retired in Taiwan.

Japanese second seed Misaki Doi moved within a victory of the final without taking to the court.

Countrywoman and seventh seed Kurumi Nara withdrew before a ball was hit.

Next up for Doi is Hsieh Su-wei, who accounted for Elizaveta Kulichkova 6-0 6-2 in just 52 minutes.