Iga Swiatek returns from rib injury to down Zheng Qinwen in Stuttgart

The world number one pulled out of the Miami Open and Billie Jean King Cup duty with Poland because of a rib injury but eased to a 6-1 6-4 success against her Chinese opponent to reach the quarter-finals of the Porsche Tennis Grand Prix.

Swiatek breezed through the opening set but was tested in the second, losing an early break of serve before breaking again to lead 5-4 and setting up a last-eight clash with Karolina Pliskova.

The Pole won this title last year as part of a 37-match winning run that included her second French Open title.

Swiatek's only defeat on clay in 2022 came on home soil in Warsaw last July to Caroline Garcia.

"I felt like I needed to be 100 per cent focused from the beginning to the end, to think about technique and tactics," Swiatek said afterwards, quoted on the WTA Tour website.

"I'm pretty happy that I'm not rusty and I could perform good tennis, even though I had a break."

Pliskova defeated Donna Vekic in a very tight encounter, prevailing 6-2 6-7 (5) 7-6 (5), while Russian Anastasia Potapova upset fifth seed Coco Gauff 6-2 6-3.

Paula Badosa progressed to a quarter-final showdown against second seed Aryna Sabalenka after a 6-1 6-2 win over fellow Spaniard Cristina Bucsa. Fourth seed Garcia saw off wild card Tatjana Maria in straight sets, 7-6 (5) 6-4, and will next face Potapova.

Wimbledon champion Elena Rybakina retired due to injury in her late match against Beatriz Haddad Maia, who was leading 6-1 3-1. The Brazilian goes on to play Ons Jabeur in the quarter-finals.