Tennis Tracker: Gauff taking on Krejcikova after Swiatek crushes Kasatkina in Riyadh
16:49 CET - Cameron Norrie's (29) impressive form in Metz shows no signs of slowing down, with the Brit seeing off Zizou Bergs (25) 6-3, 6-7(6), 6-1 to reach the final four.
Meanwhile, in Belgrade, home favourite Laslo Djere (29) is into the semi-finals after a convincing 6-4, 6-2 victory over Fabian Marozsan (25).
15:02 CET - Back to Belgrade, where Canada's Denis Shapovalov (25) has seen off Australian Christopher O'Connell (30) 6-2, 6-2 to advance into the semi-finals.
14:47 CET - Iga Swiatek (23) was in ruthless form at the WTA Finals this afternoon, sweeping aside stand-in Daria Kasatkina (27) 6-1, 6-0 in just 53 minutes.
It's the 61st win of another impressive year for the Pole, who will be hoping Coco Gauff (20) can do her a favour against Barbora Krejcikova (28) as she waits to see if she's done enough to reach the semi-finals.
Follow the second match of the day here.
13:25 CET - Fourth seed Jiri Lehecka (22) is through to the semi-finals in Belgrade after recovering from a set down to outlast Lukas Klein (26) 3-6, 7-6(3), 6-3 in just over two hours.
09:56 CET - It's a big day at the WTA Finals in Riyadh, with Iga Swiatek (23) taking on stand-in Daria Kasatkina (27) at 13:30 CET for a place in the semi-finals.
Following that match, already-qualified Coco Gauff (20) faces Barbora Krejcikova (28), as the Czech looks to join Gauff in the last four.
Elsewhere, ATP tournaments in Belgrade and Metz approach the business end of proceedings. Catch up on yesterday's action here.
09:00 CET - Good morning and welcome to our coverage of today's tennis!