Keys withdraws from WTA Finals with illness

The Australian Open champion suffered two defeats in round-robin play this week in Riyadh, to Iga Swiatek and Amanda Anisimova, and had no chance of advancing to Friday's semi-finals.

At the end of her match against Anisimova on Monday, Keys wouldn't shake her opponent's hand, indicating she was feeling unwell and didn't want to pass on the virus.

"I'm really disappointed to not be feeling my best and ultimately having to withdraw from the tournament. It's a huge accomplishment to make it this far and I'm very proud of myself for doing that and having a great year. I hope to be back next year," said Keys in a statement.

Alexandrova is the second alternate in Riyadh. The first alternate, Mirra Andreeva, who is already competing in the doubles at this year's WTA Finals, elected not to sign in due to not being fit to play on Wednesday.

Andreeva has a doubles match on Thursday, alongside her partner Diana Shnaider, and might be called in for duty as an alternate to replace Jasmine Paolini in singles, given the Italian is no longer in contention for a semi-final spot and is also feeling unwell.

Wednesday's schedule features the third and final set of round-robin matches in the Serena Williams Group, with Rybakina taking on Alexandrova and Swiatek facing off with Anisimova.

Rybakina has already secured her place in the semi-finals as the group winner, while Swiatek and Anisimova will battle it out for the other ticket to the final four.