Rafael Nadal's hopes of reclaiming the world number one spot from Roger Federer have taken a plunge, with a first up loss at the ATP world tour tennis finals in London.
Swede Robin Soderling beat Nadal 6-4 6-4 in their group B match.
A loss to Russia's Nikolay Davydenko in the second of his three round-robin matches would almost certainly rule the Spaniard out of making the semi-finals.
Soderling only made the top eight competition, through the injury enforced withdrawal of American Andy Roddick.
In today's other match Davydenko was beaten by Serbia's defending champion Novak Djokovic 3-6 6-4 7-5 in a repeat of last year's final when the season-ending climax was staged in Shanghai.