But once again, the 21-year-old was unable to sustain her momentum and broken back straight away, with inconsistency off the ground still hampering her – as well as the dreaded double faults creeping into her game at inopportune moments, with a third handing over another break to trail 3-5. Bertens, able to pump heavy topspin even from deep behind the baseline, was increasingly impregnable on defence, much to Ostapenko’s frustration, who ended the day with 30 unforced errors to 14 winners.

But the St. Petersburg champion was also sharp in her awareness of when to take charge, even against her ultra-aggressive opponent, ending with 20 winners to a mere 10 unforced errors. The Bertens backhand in particular was a thing of beauty in the closing stages as the 27-year-old seized control to reel off 12 of the last 14 points from 3-3 in the second set, winning her the best point of the match in the final game – a pinpoint winner down the line after some dogged defensive work.

Up next for Bertens in her quest to make a third consecutive quarterfinal in Madrid will be either No.12 seed Anastasija Sevastova or Mihaela Buzarnescu.