Naomi Osaka upset No 4 seed Elise Mertens 6-2, 6-4 in the first round at the Libema Open, notching her first win on grass since 2019 on Tuesday in 's-Hertogenbosch, Netherlands.

Osaka, the former World No 1 and four-time Grand Slam champion from Japan, fired seven aces and saved the only break point she faced against Belgium's Mertens in the 69-minute victory.

ALSO READ: Clay queen Swiatek rules again at Roland Garros

In other action involving seeded players, No 1 Jessica Pegula defeated Belarusian Aliaksandra Sasnovich 6-2, 6-2 and No 3 seed Ekaterina Alexandrova of Russia was a 6-3, 6-4 winner against Australia's Arina Rodionova. Sixth-seeded Yuan Yue of China rallied for a 1-6, 6-4, 6-3 defeat of Russia's Diana Shnaider. A match between eighth-seeded Magda Linette and Robin Montgomery was suspended at 5-5 in the third set. Linette took the first set 7-6 (4), and Robinson claimed the second set 6-3.

READ MORE: Swiatek, Paolini set up Paris final showdown

Rothesay Open

Britain's Emma Raducanu rolled to a 6-1, 6-4 victory against Japan's Ena Shibahara in the opening round in Nottingham, England.

After skipping the French Open to prepare for the grass-court season, Raducanu converted six of eight break chances. The 2021 US Open champion faltered briefly after taking a 5-1 lead in the second set but finished in 70 minutes.

READ MORE: Big guns Swiatek and Osaka meet in early French Open showdown

No 1 seed Ons Jabeur of Tunisia opened with a 6-2, 6-3 win over Colombia's Camila Osorio and No 5 seed Magdalena Frech of Poland defeated Japan's Nao Hibino 6-1, 6-4. Two other seeded players made an early exit, with No 2 Marta Kostyuk losing 6-3, 6-3 to fellow Ukrainian Daria Snigur and No 8 Caroline Dolehide losing 7-6 (3), 6-3 to Britain's Francesca Jones.