Aryna Sabalenka upsets second seed Ons Jabeur on opening night of WTA Finals

Maria Sakkari also defeated a higher seeded player as the tournament began in Texas

Aryna Sabalenka outlasted second seed Ons Jabeur 3-6 7-6 (5) 7-5 over almost two-and-a-half hours on the opening night of round-robin play at the WTA Finals (Tim Heitman/PA) (AP)

Aryna Sabalenka outlasted second seed Ons Jabeur 3-6 7-6 (5) 7-5 over almost two-and-a-half hours on the opening night of round-robin play at the WTA Finals.

The seventh seed battled back when down 5-3 in the second set tiebreak and again while at 5-2 in the third set to defeat Wimbledon and US Open finalist Jabeur, who was on debut at the tournament in Fort Worth, Texas.

It marked the fourth career defeat of a top two player by the Belarusian, who joined Maria Sakkari in leading the Nancy Richey Group following the first night’s competition.

Sakkari, who secured the last spot at the tournament with a victory at last month’s Guadalajara Open, mounted her own upset with a 7-6 (6) 7-6 (4) victory over third seed Jennifer Pegula.

The Greek fifth seed survived two tiebreakers at Dickies Arena for the result, which came as revenge after she lost the final to the American in Guadalajara eight days earlier.

Sakkari said after the match: “I was very aggressive. If you’re passive, Jess is just going to make you run – she’s going to hit the ball very hard, and it’s over.”