Sabalenka secured the year-end world number one ranking this week after a stellar season, but she was frustrated, error-prone and annoyed throughout against Gauff.
Her forehand faltered – such a crucial component of her game – with 16 unforced errors coming off it in the first set.
She and Gauff traded breaks early on but Gauff was serene on serve, able to extend the rally in the knowledge that Sabalenka would eventually hit an error.
Despite the chaos, Sabalenka broke for a 6-5 lead and served for the set, but a netted backhand sent it to a tie-break, which Gauff dominated.
After a lengthy bathroom break, Sabalenka started the second set better but another backhand miss hurried Gauff to an early break.
Gauff reeled off four games in a row for a 4-1 lead before Sabalenka eventually retrieved one of the breaks – but she needed eight break points to do that after a mammoth Gauff service game.
Given the erratic nature of the match, a break of the Sabalenka serve in the next game felt inevitable, and it was – as was Gauff being broken when she served for the match at 5-2.
But Sabalenka could not delay the inevitable even on her serve, and a final netted backhand – her 37th unforced error of the night – secured victory for Gauff.
