ATP World Tour finals: day four

LONDON, ENGLAND - NOVEMBER 25: Rafael Nadal of Spain arrives with the mascot during the men's singles first round match against Nikolay Davydenko of Russia during the Barclays ATP World Tour Finals at the O2 Arena on November 25, 2009 in London, England. (Photo by Matthew Lewis/Getty Images for Barclays ATP Finals) Tennis Photograph: Matthew Lewis/guardian.co.uk

LONDON, ENGLAND - NOVEMBER 25: Nikolay Davydenko of Russia serves during the men's singles first round match against Rafael Nadal of Spain during the Barclays ATP World Tour Finals at the O2 Arena on November 25, 2009 in London, England. (Photo by Julian Finney/Getty Images) Tennis Photograph: Julian Finney/guardian.co.uk

LONDON, ENGLAND - NOVEMBER 25: Rafael Nadal of Spain serves the ball during the men's singles first round match against Nikolay Davydenko of Russia during the Barclays ATP World Tour Finals at the O2 Arena on November 25, 2009 in London, England. (Photo by Clive Brunskill/Getty Images) Tennis Photograph: Clive Brunskill/guardian.co.uk

Rafael Nadal of Spain reacts during his ATP World Tour Finals tennis match against Nikolay Davydenko of Russia in London November 25, 2009. REUTERS/Suzanne Plunkett (BRITAIN SPORT TENNIS) :rel:d:bm:GF2E5BP1TFY01 Photograph: Suzanne Plunkett/guardian.co.uk

Russia's Nikolay Davydenko returns a ball during his ATP World Tour Finals tennis match against Spain's Rafael Nadal at the O2 Arena in London, Wednesday Nov. 25, 2009. (AP Photo/Kirsty Wigglesworth) Photograph: Kirsty Wigglesworth/guardian.co.uk

Spain's Rafael Nadal returns the ball to Russia's Nikolay Davydenko during their ATP World Tour Finals tennis match at the 02 Arena in London, Wednesday, Nov. 25, 2009. (AP Photo/Sang Tan) Photograph: Sang Tan/guardian.co.uk

Rafael Nadal of Spain plays against Nikolay Davydenko of Russia in a Singles match during the Barclays ATP World Tour Tennis Finals in London, on November 25, 2009. AFP PHOTO/GLYN KIRK (Photo credit should read GLYN KIRK/AFP/Getty Images) HORIZONTAL Photograph: Glyn Kirk/guardian.co.uk

Russia's Nikolay Davydenko returns the ball to Spain's Rafael Nadal during their ATP World Tour Finals tennis match at the 02 Arena in London, Wednesday, Nov. 25, 2009. (AP Photo/Sang Tan) Photograph: Sang Tan/guardian.co.uk

Spain's Rafael Nadal reacts during his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Wednesday Nov. 25, 2009. (AP Photo/Kirsty Wigglesworth) Photograph: Kirsty Wigglesworth/guardian.co.uk

epa01945192 Robin Soderling of Sweden returns the ball to Serbia's Novak Djokovic during an ATP Masters Tennis match at the O2 Arena in London, Britain, 25 November 2009. Soderling won 7-6, 6-1. EPA/ANDY RAIN Photograph: Andy Rain/guardian.co.uk

Novak Djokovic stretches for a point during his loss to Robin Soderling during the ATP World Tennis Tour Finals at the o2 Arena Photograph: Adam Davy/guardian.co.uk

epa01945230 Robin Soderling of Sweden reacts after his win over Serbia's Novak Djokovic during an ATP Masters Tennis match at the O2 Arena in London, Britain, 25 November 2009. Soderling won the match 7-6, 6-1. EPA/ANDY RAIN Photograph: Andy Rain/guardian.co.uk

Novak Djorkovic reacts to losing the first set to Robin Soderling during the ATP World Tennis Tour Finals at the o2 Arena Photograph: Adam Davy/guardian.co.uk

Serbia's Novak Djokovic throws a towel over his shoulder during his ATP World Tour Finals tennis match against Sweden's Robin Soderling at the 02 Arena in London, Wednesday, Nov. 25, 2009. (AP Photo/Sang Tan) Photograph: Sang Tan/guardian.co.uk