Radwanska withdraws in Tianjin

Simona Halep beats Venus Williams in straight sets at the Miami Open

Top seed Agnieszka Radwanska was forced to withdraw from the Tianjin Open with a right thigh strain on Friday.

While the world number three did not say as much, she appeared to have the year-end WTA finals on her mind.

"I'm very sorry I had to withdraw…I just hope I can see my fans [here] next year," said the Pole.

"It was a pleasure to come here again."

Radwanska's withdrawal gives Shuai Peng a free run into the semi-finals without a shot being played. 

The Chinese native will match up against Danka Kovinic, who knocked out fifth seed Monica Puig 6-4, 6-3 later in the day.

In other results, Alison Riske advanced to the final four following her straight set 6-3, 6-3 win over Xin-Yun Han. 

The American will face second seed Svetlana Kuznetsova, who rallied back from a set down to defeat Naomi Osaka in a three set thriller lasting over two hours in the final match of the day.