Dominika Cibulkova scored an upset victory over Angelique Kerber to claim the WTA Finals title on Sunday, beating the world number one 6-3 6-4.
Cibulkova, runner-up in the 2014 Australian Open, turned the tables on Kerber just a week after losing to her in the round-robin stage and captured the biggest title of her career in Singapore.
Cibulkova upsets the odds
Kerber went into the final as overwhelming favourite after taking this year's Australian Open and US Open titles. But the 28-year-old was powerless to stop the diminutive Slovakian, who has made an inspired return to the game's elite and was named the WTA's Comeback Player of the Year.
Cibulkova was facing an early exit when she lost her first two round-robin matches in Singapore. But she won her last three matches to receive the Billie Jean King trophy and a cheque for $2.05 million, the biggest payday of her life.
Makarova, Vesnina win doubles
In the doubles finals Russian Olympic champions Ekaterina Makarova and Elena Vesnina beat US Open winners Bethanie Mattek-Sands and Lucie Safarova 7-5 (7-5) 6-3.
After the start was delayed by 30 minutes due to a lighting problem, Makarova and Vesnina began the first set by conceding two games. But they fought back in a closely contested encounter which saw 14 break points and three match points.
Each time they pulled ahead, Mattek-Sands and Safarova caught up quickly.
But Makarova and Vesnina dug deep to take the first set on a tie break. They went on to dictate the second set and were handed the title due to a service error from Mattek-Sands.
Their victory in the season-ending tournament, open only to the top eight doubles pairs, rounds off a remarkable year in which they reached the finals of the French Open and won Olympic gold.
"This year for us is just amazing," Vesnina said.
The pair were presented with the Martina Navratilova Doubles Trophy at the Singapore Indoor Stadium by the tennis legend in person.
Makarova and Vesnina, who have been playing together since 2012, have seven doubles titles as a team, including the US Open in 2014 and the French Open in 2013.
Makarova is left-handed while Vesnina uses her right hand, a feature which Vesnina described as their winning combination.
"When we're motivated, ready and healthy, we're a very dangerous team," she said.