Jessica Pegula upset world number one Aryna Sabalenka 6-4 6-3 to win her second group stage match at the WTA Finals in Cancun on Tuesday and advance to the semi-finals. The American, who won her first round-robin match by beating Elena Rybakina on Sunday night, dominated her out-of-sorts Belarusian opponent from the outset and punished every error. Pegula, who came into the contest with a dismal 1-4 record against the hard-hitting Sabalenka, managed to absorb her powerful serve to extend rallies and thwart the Belarusian’s comeback attempts.

Pegula took a two-game lead in the opening set and won five of the first six games in the second. A run of four consecutive breaks in the fifth game gave her a 7-2 lead. Sabalenka, who lost her first two matches of the year in straight sets, had some hope of a comeback after she held for a 3-1 lead but double-faulted on her first match point to leave herself vulnerable to a third.

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It was the first time that Sabalenka had lost on a match point in her career, and she saved a further five before finally succumbing to the seventh when she shanked a backhand to hand Pegula a 6-2 6-3 victory in just over an hour. Pegula, who has won 43 matches on a hard court this season, including five against top-10 players, said afterward that she is happy to be through to the last four after starting the week with just two points in the round-robin standings.

Pegula will play the winner of Wednesday’s match between Rybakina and Sakkari in her final group stage match on Thursday and is assured of finishing top of the Bacalar Group if she can avoid defeat by the Belarusian. Having already won more match wins than the current year-end leaders Leylah Fernandez and Serena Swiatek, Pegula needs two more victories in the remaining rounds to guarantee the year-end top spot.

The other top-half matches on Tuesday include sixth seed Coco Gauff playing 2017 French Open runner-up Jelena Ostapenko and No 10 Karolina Muchova facing Sorana Cirstea. The doubles match of the day features No. 2 seeds Shuko Aoyama & Ena Shibahara against Desirae Krawczyk and Demi Schuurs of the Netherlands.