BERLIN –

Four-time Grand Slam winner Naomi Osaka tumbled out of the Berlin Open in the first round on Tuesday after Russia's Liudmila Samsonova battled from a set down to win 3-6, 7-6 (3), 6-4.

It was a disappointing start to the former world No. 1's grass season, with Wimbledon starting in just under two weeks. The 27-year-old has struggled to regain her previous elite form following a maternity break.

Osaka, who had reached the third round of the Australian Open in January before retiring injured, also lost in the first round of the French Open.

After a strong start from Osaka, Samsonova battled back in the second set to clinch the frame in a tiebreak.

Osaka was 40-0 up on her opponent's serve at 5-5 but could not finish the job and allowed her to come back.

"I was just trying to fight until the end," said Samsonova, a winner in Berlin four years ago.

"I said, 'OK, until the last ball, I will try to push and try to find my game.'"

She did just that to set up a round of 16 match against the third-seeded Jessica Pegula.

Australian Open champion and seventh seed Madison Keys also suffered an early exit, with Czech Marketa Vondrousova, the 2023 Wimbledon champion, moving into the next round with a 7-5, 7-6 (6) win.

Vondrousova, who had been out for three months earlier this year with a shoulder injury, will face Diana Shnaider in the round of 16 after the 21-year-old Russian overran Croatia's Donna Vekic 6-2, 6-4.

The southpaw powered through the first four games and, before Vekic had any time to react, she had wrapped up the first set with her fourth set point.

Shnaider then found a bit more resistance with her opponent earning early break only to be immediately broken back twice as the world No. 12 bullied Vekic with punishing groundstrokes to go 5-4 up and seal the win on Vekic's serve.

China's Wang Xinyu had to do even less work, matching world No. 16 Daria Kasatkina's baseline game blow for blow, to drop just five games en route to a 6-3, 6-2 victory in 67 minutes.

She will next play French Open champion and second seed Coco Gauff.

Fellow Chinese and fifth seed Zheng Qinwen pulled out on Tuesday with a right neck injury ahead of her match against Elena Rybakina with American Ashlyn Krueger slipping in as a lucky loser.