London: Rafael Nadal suffered a straight-set loss to defending champion Alexander Zverev at the ATP Finals opener on Monday.
With this, Alexander Zverev tasted the first victory.
The Spaniard was beaten 6-2 6-4 in their opening round-robin match. Nadal, who has not completed a tournament since September’s US Open, was out of sorts and error-prone.
Earlier, sixth seed Stefanos Tsitsipas beat fellow debutant Daniil Medvedev. The Greek 21-year-old beat the Russian 7-6 (7-5) 6-4 at the O2 Arena.