Jessica Pegula beats Gauff 6-3, 6-7 (4), 6-2

World No 1 Sabalenka defeats Paolini in earlier match

Coco Gauff’s serving woes followed her into the final week of the season, as the American’s title defence at the WTA Finals in Riyadh began with a bruising 6-3, 6-7 (4), 6-2 loss to her compatriot Jessica Pegula in their first match of the group stages.

Despite fighting hard and remaining competitive until the end, the third seed simply could not overcome her 17 double faults against an in-form Pegula, the fifth seed, who maintained her composure after getting pulled into a final set by her struggling opponent, and saved her best level for the closing stretch of the match.

Pegula’s victory could prove to be an important win in the Stefanie Graf group, with Aryna Sabalenka looming and favoured to advance. Earlier on Sunday, the world No 1 opened her tournament with a confident 6-3, 6-1 win over Jasmine Paolini, the eighth seed. The victory was Sabalenka’s 60th of the season, the first time she has achieved this milestone.