2019 Nitto ATP Finals
Venue: O2 Arena, London
Dates: Nov 10-17
Stefanos Tsitsipas reached the semi-finals of the ATP Finals, while Rafael Nadal produced a stunning comeback to boost his hopes of joining him.
Tsitsipas, 21, making his debut at the event, dominated defending champion Alexander Zverev in a 6-3 6-2 win.
Earlier, Nadal fought back from 5-1 down in the deciding set and saved a match point to beat fourth seed Daniil Medvedev 6-7 (3-7) 6-3 7-6 (7-4).
The Spaniard must beat Tsitsipas on Friday to have a chance of advancing.
Nadal, who is also looking to keep hold of the world number one ranking, could have been eliminated on Wednesday had he lost and his fate is still not in his own hands as he also needs Medvedev to beat Zverev in their match on Friday.
Nadal, 33, admitted he got "super lucky" to beat the Russian.