By Caroline Cheese
BBC Sport at the O2 Arena
Robin Soderling caused his second upset of the ATP World Tour Finals as he saw off defending champion Novak Djokovic in straight sets.
The Swede, a late replacement for Andy Roddick, prevailed 7-6 (7-5) 6-1 to guarantee his place in Saturday’s semi-finals.
Djokovic came into the tournament as the form player after a run of 17 wins in 18 matches, but after edging out Nikolay Davydenko in his opening Group B match, the Serb complained of tiredness - and he looked sluggish throughout against Soderling.
After missing out on two break points at 1-1, Djokovic’s shoulders slumped, and he continually vented his frustrations at his support camp.
606: DEBATE
“Excuses time, Djokovic was clearly tired!!! No seriously, well played Soderling, he played very well”
**Always United **
At 5-4, the world number three bravely saved three set points, but Soderling would not be denied.
The eighth seed, whose serve was outstanding throughout, appropriately sealed a tight tie-break with a big first serve.
Djokovic spent the changeover muttering to himself, and he could not lift himself in the second set.
Soderling, thriving in his favourite indoor conditions, reeled off six games in a row on his way to a superb win after one hour and 34 minutes, maintaining his record of being the only player in London not to drop a set.
The Swede will face Nikolay Davydenko in his final match on Friday, while Djokovic takes on Rafael Nadal.
Nadal meets Davydenko later on Wednesday.