Although the one-sided nature of the first set would be a thing of the past, it was evident that Bertens was scrambling to keep up with Pavlyuchenkova as they shared the opening four games of the second.
In the fifth, though, Pavlyuchenkova reprised the devastating hitting she displayed so amply in the first set. A crushing backhand down the line sealed a break to 15.
It was a moment that was the catalyst for seven breaks in succession. Faced with the prospect of a opening-match exit for just the fourth time in 2019, Bertens became more energetic and more aggressive.
Her approach was typified by a forehand loaded with topspin that kissed the outside of the tramline to win that initial break back, but she was stuttering with her serve and lost two successive marathons on her own delivery.
Pavlyuchekova managed to get to within a point of victory on serve but unsuccessfully challenged a shot that had drifted long, then fired another two shots out of court to be broken.
It proved, however, a case of fourth time lucky as she again had success on her opponent’s delivery before sealing the match and a quarterfinal date with in-form Japanese wildcard Misaki Doi as she finally held.
Doi had earlier caused an upset of her own by defeating No.7 seed Donna Vekic, 7-6(5), 6-3. The WTA World No.83 saved successive set points on her opponent’s serve in the first set, which she went on to win in a tiebreak. With Vekic struggling on her delivery, she was broken three times in the second.
Yulia Putintseva was also a winner in two sets, defeating Varvara Flink, 6-1, 6-1 in just 73 minutes.