World number one Aryna Sabalenka secured a semi-final berth at the WTA Finals by beating Italian fourth seed Jasmine Paolini 6-3 7-5 on Monday to stay unbeaten in the purple round-robin group.

The 26-year-old is on the brink of clinching the year-end number one ranking. A win over Elena Rybakina in the final group match on Wednesday or a loss from her rival, Poland's Iga Swiatek, would seal the year-end top spot for the Belarusian.

Sabalenka's win combined with Chinese Zheng Qinwen’s earlier 7-6(4) 3-6 6-1 victory over Rybakina ensured the top seed will finish first in her group regardless of her final result on Wednesday, making her the first player to reach the final four.

Australian Open and US Open champion Sabalenka also won her opening match in Riyadh against seventh seed Zheng. The Chinese player and Paolini, with 1-1 records, both remain in contention for the semis and meet on Wednesday.

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Swiatek is the only player who can overtake Sabalenka. The 23-year-old, who plays Coco Gauff on Tuesday, needs to retain her title undefeated and hope Sabalenka loses her remaining matches in order to claim the year-end number one spot.

"I’m proud of myself. Not only myself, my team," Sabalenka said after her win. "We were able to overcome a lot of things. To be able to show such great tennis and become world number one, It’s teamwork. It’s not only me."

"Nobody sees the behind the scenes work. But they do a lot for me. I really appreciate them for everything they do for me. This is motivation for me to keep winning on this court. Those guys deserve to be called the best team ever."

READ MORE: Zheng Qinwen loses opening match to Sabalenka at WTA Finals

Sabalenka is the first player to reach back-to-back semis at the WTA Finals as world number one since Serena Williams in 2013-2014.