She finished with 16 winners and only six unforced errors, a margin that showed how cleanly she struck the ball after the early scrambling.
The win stood out because Sabalenka, the second seed, had been in control early and then barely stayed in the points. From the moment she held that double-break lead, she won only 10 more points in the match.
Andreeva changed the set by serving three aces in a row. She took the lead and never looked back, going on to win the first set 6-4.
The second set was one-sided. Andreeva won it 6-0, giving Sabalenka no foothold once the first-set lead had gone.
Andreeva began by using loopy, high balls to wrong-foot Sabalenka. She followed that with easy power and brilliant angles from the baseline.
Sabalenka played with tape on her knee. The support did not seem to hinder her movement. The loss looked instead like some of the collapses she has had this year.
Poor as Sabalenka was on the day, Andreeva answered with a mature, intelligent performance and shut her out of the match.
"I will be honest, I feel like Aryna did not have the best day,"Andreeva told Sky Sports.