Alexander Zverev has beaten Rafael Nadal in their opening round-robin match of the ATP Finals.
The loss dents Nadal's chances of ending the year as the number one ranked tennis player in the world.
He entered the season-finale in London with an abdominal injury.
Tuesday's match sees Roger Federer, who also lost his opening encounter, take on Italy's Matteo Berrettini.
Play gets underway at 6:00 pm UAE time.
Liverpool eliminated as Atalanta book Europa League semi-final place
Atalanta progressed to the Europa League semi-finals despite losing 1-0 to Liverpool on Thursday as they triumphed 3-1 on aggregate to move one step closer to a first ever European final for the Serie A side.
Real Madrid knock out holders Man City in Champions League shootout
Antonio Ruediger scored the decisive penalty as Real Madrid beat holders Manchester City in an edge-of-your-seat 4-3 shootout victory to reach the semi-finals of the Champions League after the teams were locked at 4-4 on aggregate following extra time on Wednesday.
Kimmich heads Bayern Munich past Arsenal and into semi-finals
Bayern Munich's Joshua Kimmich powered in a 63rd-minute header to give them a 1-0 victory over a toothless Arsenal on Wednesday and send them through to the Champions League semi-finals for the first time in four years with a 3-2 aggregate win.
Nadal makes winning return in Barcelona
Rafael Nadal said it was a challenge to hold himself back on his return to the ATP Tour after three months on the sidelines but the fiercely-competitive Spaniard expects to continue with the controlled approach in Barcelona.
Mbappe scores twice as PSG beat 10-man Barca to reach semi-finals
Paris St Germain's Kylian Mbappe scored twice in the second half to help his side to a 4-1 comeback win at 10-man Barcelona in their Champions League quarter-final, second leg to wrap up a 6-4 aggregate victory on Tuesday.
