When Aryna Sabalenka and Coco Gauff stared each other down just a month ago in Wuhan, Gauff clearly had the edge as she methodically established a set and break lead. But then, out of nowhere, her serve spectacularly crumbled. Although she fought valiantly until the end, she was torpedoed by an astounding 21 double faults.

Having already been a presence on the tour for half a decade, it is sometimes easy to forget that, at 20 years old, Gauff is still growing, still a work in progress. Throughout this week, the American has shown the results of some of that progress as she arrived in Riyadh with significant adjustments in her game and she has used them to play some of the best tennis of her career. On Friday, Gauff produced a superb performance against Sabalenka, the world No 1, to reach the final of the WTA Finals with a spectacular 7-6 (4), 6-3 win.

In the final, Gauff will face Zheng Qinwen, the Olympic gold medallist, in a tussle between the two youngest players in the top 10. Zheng extended her magnificent breakout season by reaching the final round of the WTA Finals for the first time in her career, holding off a spirited comeback from the Wimbledon champion, Barbora Krejcikova, before closing out a tough 6-3, 7-5 win. The 22-year-old will rise to a new career high ranking of at least No 5 after her performances in Saudi Arabia.

Throughout Gauff’s short career, no aspect of her game has been under more scrutiny than her forehand, which she strikes with an extreme western grip and has often been vulnerable against the best players in the world. This week, though, Gauff’s weaker groundstroke has been extremely solid. After splitting with her former coach Brad Gilbert after the US Open and hiring Matt Daly in his place, Gauff has also changed her grip in her service motion.

Those improvements were all clear in her rematch against the best player in the world, Sabalenka. In a scrappy opening set, Gauff served well and soaked up Sabalenka’s immense pace brilliantly with her forehand, maintaining consistent depth throughout. She made the court seem so narrow for Sabalenka with her remarkable defence. Although Sabalenka served for the set, Gauff retrieved the break before playing an extremely clean tie-break and then refusing to relinquish her momentum. This time, she struck just two double faults throughout.

Over the past few months, Sabalenka has played the best tennis of her career. She won her third grand slam title at the US Open, plus the WTA 1000 events in Cincinnati and Wuhan, winning 21 of 22 matches in the process. For once, however, she looked tired and tense as she failed to match Gauff’s intensity. This year has marked the best season of her career, but Sabalenka finishes 2024 with a tough loss.

Meanwhile, Zheng’s run to the final in Riyadh is the result of a remarkably consistent spell of form since this summer. Despite reaching her first grand slam final at the Australian Open this year. Zheng’s true breakthrough came as she clinched an Olympic singles gold medal in Paris, pulling off an incredible upset win against Iga Swiatek en route, and since then her momentum has only continued to grow. After compiling a 31-5 record since mid-July, Zheng will aim to close off a spectacular season with another significant title.