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Having played her first-round matchup – a 6-4 6-1 win over Magdalena Frech – across two days due to a rain delay, Osaka was determined to ensure swift progression.

She only needed 67 minutes to eliminate the world number 21, setting up a potential last-eight showdown with French Open champion and second seed Mirra Andreeva.

Osaka started as she meant to go on by winning the first five games, and although a small wobble saw Mertens claw the opening set back to 5-3, the four-time grand slam champion recovered her composure to serve it out.

And nothing truly changed in the second set as Osaka continued to dictate proceedings, getting a break in game three then threatening another in game seven, as Mertens was forced to save four break points. 

Having only given up four points on serve throughout the second set, Osaka got the job done by impressively breaking again to love.

She will be joined in the last eight by Emma Navarro, who defeated Eva Lys in straight sets earlier on Tuesday, and Xin Wang, who got past Leylah Fernandez. 

Elena-Gabriela Ruse also advanced by upsetting Berlin Open champion Linda Noskova 6-1 6-3, while Ekaterina Alexandrova edged out Ann Li 6-1 6-7 (5-7) 6-1.