Nikolay Davydenko beat Robin Soderling 7-6 (7/4) 4-6 6-3 tonight to book his place in the semi-finals of the Barclays ATP World Tour Finals at London's O2 Arena.

After yesterday's shenanigans, the equation tonight was simple - a win for the Russian would put him through while defeat would hand the second semi-final spot to Novak Djokovic, who beat Rafael Nadal earlier.

Davydenko proved up to the task but the set Soderling won ensured he topped the group and will meet Juan Martin del Potro tomorrow evening, while the world number seven faces a quick turnaround for an afternoon match against Roger Federer.

Soderling had been hugely impressive in his wins over the world number two and three in Group B and he again looked extremely solid, easily holding serve in the early stages.

The Swede came under pressure for the first time in the seventh game but he saved the first break point of the match courtesy of a big serve.

Soderling had chances of his own to forge ahead a game later but this time it was Davydenko who was equal to the challenge and the set would be settled on a tie-break.

The eighth seed struck first, edging a titanic rally, but he let two service points slip away and Davydenko wrapped up the set with a simple smash.

Soderling looked fired up despite knowing his semi-final place was assured - the chance to avoid Federer in the last four possibly all the motivation he needed.

But Davydenko, who lost last year's final to Djokovic, was having no trouble matching the Swede's power, and he engineered the first break point of the second set in the sixth game when Soderling netted.

He could not take it, though, and instead it was the world number nine who claimed the first break of the match.

Soderling took a heavy fall in the eighth game but he took it in his stride and strung together a series of brilliant points to break to love. Serving out the set proved no problem, either.

Soderling would have been confident going into the final set, having beaten Davydenko six times from nine meetings, including in three sets in Paris earlier this month.

But the Swede was in trouble in the sixth game, slipping to 0-40, and Davydenko needed only one chance as Soderling thrashed a wild forehand long.

He double-faulted on his first match point but took his second chance when Soderling inexplicably thrashed a forehand well long.

Davydenko said: "It's a great day for me. Soderling played very well but I knew I needed to win today and I did."