Newly crowned French Open champion Coco Gauff has been stunned on her return to action following her French Open victory, losing to Chinese qualifier Wang Xinyu 6-3 6-3 at the Berlin Open.

World No.2 Gauff, who won at Roland Garros less than two weeks ago for her second grand slam title, amassed 25 unforced errors and seven double faults in her loss to Wang on Thursday.

Gauff had a bye to the second round at the grass-court tournament, a warm-up for Wimbledon.

Wang, ranked No. 49, said she would have been pleased just with the first set, considering the level of her opponent.

"After I won the first set, I just told myself, 'okay, let's take a minute and enjoy this, I'm playing the French Open champion, and I won the first set'," said Wang, who next plays Spain's eighth-seed Paula Badosa.

"No matter how the second and third go, I was like, 'okay, let's just enjoy it for a second.' I'm really happy with how I played today. I was serving good and putting a lot of pressure on the return, especially second-serve return."

Aryna Sabalenka, also playing for the first time since losing to Gauff in the Paris final, completed a 6-2 7-6 (8-6) win over Swiss Rebeka Masarova to reach the quarter-finals, concluding a match that had been suspended on Wednesday because of slippery conditions.

When the match resumed, world No.1 Sabalenka was broken at the start of the second set and found herself 3-1 and 4-2 down.

She kept her cool, however, and broke back with a fine volley to force a tiebreak.

Sabalenka also squandered two match points before sealing her victory at her next opportunity when her opponent sank a simple mid-court forehand into the net.

The top seed will next face former Wimbledon champ Elena Rybakina.

Czech Marketa Vondrousova, the 2023 Wimbledon champion, needed three sets over two hours and 20 minutes to break the resistance of Russia's Diana Shnaider 6-3 6-7 (3-7) 6-3 win and will face lucky loser Ons Jabeur, the two-time Wimbledon finalist, in the last eight.

At the Nottingham Open grass-court event, two-time defending champion Katie Boulter, the fiancee of Australian No.1 Alex de Minaur, was given a real scare before battling past fellow Briton Sonay Kartal 6-4 1-6 7-5 to reach the quarter-finals.