World number one Elena Rybakina has withdrawn from the WTA Finals because of a viral illness.

Rybakina triumphed at the Australian Open and the US Open in a stellar 2026 as she established herself as the top-ranked women's singles player for the first time.

She was set to begin her bid to emulate American great Serena Williams by becoming the first player since 2014 to win the WTA Finals in back-to-back years on Sunday.

But the 27-year-old Kazakh announced on the eve of the tournament that she would not be able to defend her title in Indian Wells.

"I am really sad to inform all my fans and supporters that I unfortunately have to withdraw from the WTA Finals this year," Rybakina said.

"I've had an incredible season but my body is just not physically ready to compete.

"I'm going to spend some time resting and recovering at home and getting myself ready for the 2027 season."

Rybakina secured her position as the year-end world number one while competing in Tokyo in October.

She had ended Sabalenka's 99-week hold on the top ranking by defeating the Belarusian in the US Open final six weeks earlier.

This season has been the most successful of Rybakina's career, following successes at the Australian Open, US Open, Stuttgart and Ningbo. She also finished runner-up at Indian Wells and Toronto.

Rybakina has won six of her 15 career titles since last October amid a period of sustained success, during which she ended a nearly four-year wait to back-up her maiden slam title at Wimbledon in 2022.

She ends the season having won 54 of her 68 matches, including 17 of 19 in Grand Slam tournaments.

Rybakina's dominance has been founded in tour-leading serve statistics - she landed 438 aces this season, 140 more than second-placed Sabalenka.

But she has also punished opponents with an unrivalled 1,775 winners, and stepped up to the big occasions to record an unmatched 10 wins against fellow top-10 rivals.