Defending champion Agnieszka Radwanska withdrew from the Tianjin Open due to a thigh strain after taking just over an hour to beat Evgeniya Rodina in the second round.

The top seed outclassed the world number 103 from Russia, easing to a 6-1 6-1 victory in only 64 minutes on Thursday, but then abruptly pulled out of the tournament after the match.

Radwanska, who was eyeing back-to-back titles after winning the China Open on Sunday, did not appear to be troubled as she secured five breaks and won 84 per cent of points on her first serve in a one-sided second-round encounter.

But the Pole's withdrawal means she is still not assured of a place in the season-ending WTA Finals in Singapore.

Olympic champion Monica Puig made it through to the last eight with a 6-4 6-2 triumph over Lara Arruabarrena.

The fifth seed from Puerto Rico trailed 3-1 in the opening set, but got into her stride and sealed victory after breaking the Spaniard on seven occasions.

Alison Riske, winner of the inaugural 2014 Tianjin Open, also needed just the two sets to see off Magda Linette 6-3 7-6 (7-2), while home favourite Shuai Peng got the better of qualifier Kai-Chen Chang and goes straight through to the semi-finals due to Radwanska's exit.