Iga Swiatek is through to the quarter-finals of the Stuttgart Open after easing to a 6-1 6-4 win over Zheng Qinwen on her return from a rib injury.

Swiatek had not played since sustaining the issue in the semi-finals of Indian Wells over a month ago, but advanced on Thursday despite stating that she felt "rusty".

The world number one won 84 per cent of points after landing her first serve in as she made up for lost time.

Swiatek also forced eight break points, winning four of them as she took just and hour and 26 minutes to set up a quarter-final with Karolina Pliskova, who bested Donna Vekic in a thriller.

Pliskova looked to be on her way to a routine win as she claimed the first set 6-2, only for the Croatian to take the second via a tie-break.

The decider also went the distance, with Pliskova able to finally put Vekic away 6-2 6-7 (5-7) 7-6 (7-5) to book her clash with Swiatek.

Coco Gauff perhaps paid the price for taking almost three hours to beat Veronika Kudermetova on Wednesday, as the fifth seed fell to a straight-sets loss to Anastasia Potapova on Thursday, going down 6-2 6-3.

Fourth seed Caroline Garcia will go up against Potapova next after she defeated Tatjana Maria 7-6 (7-5) 6-4, while Paula Badosa had few problems seeing off fellow Spaniard Cristina Bucsa 6-1 6-2 and will face second seed Aryna Sabalenka in the last eight.