Former World No.1 Karolina Pliskova deemed tonight one of her best-ever serving days after saving all 10 break points faced against defending BNP Paribas WTA Finals Singapore presented by SC Global champion Caroline Wozniacki.

A day of upsets put Elina Svitolina and Karolina Pliskova on the brink of qualifying for the semifinals, while Caroline Wozniacki and Petra Kvitova have to fight to stay in. Here's what has to happen on Tuesday.

Defending champion Caroline Wozniacki shrugged off a tight two-set loss to rival Karolina Pliskova, aiming to come back strong on Tuesday night against Petra Kvitova.

Karolina Plsikova saved all 10 break points she faced to defeat defending champion Caroline Wozniacki in the second match from the White Group on the opening day in Singapore.

Relive the WTA Insider Live Blog from the White Group as defending champion Caroline Wozniacki faced Karolina Pliskova at the BNP Paribas WTA Finals Singapore presented by SC Global in a rematch of the 2017 semifinals in their opening match.

Former BNP Paribas WTA Finals Singapore presented by SC Global champion Petra Kvitova conveyed encouraging optimism despite a straight-set loss to Elina Svitolina, eager for a chance to make it out of round robin play.

No.6 seed Elina Svitolina served notice after a straightforward win over nemesis Petra Kvitova, and soldiered through post-match press despite suddenly feeling unwell at the BNP Paribas WTA Finals Singapore presented by SC Global.

No.6 seed Elina Svitolina ended a seven-match losing streak against No.4 seed Petra Kvitova to open the BNP Paribas WTA Finals Singapore presented by SC Global with a straight-set victory.

Relive the WTA Insider Live Blog action as Elina Svitolina claimed the first win at the 2018 BNP Paribas WTA Finals Singapore presented by SC Global over 2011 champion Petra Kvitova.

2018 WTA Player of the Year Simona Halep reflects on her emotional and physically demanding 2018, which saw her put together her best campaign yet.