Tennis Tracker: Swiatek taking on Kasatkina at WTA Finals, Lehecka through in Belgrade
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!