World No. 1 Rafael Nadal is in prime position to qualify for the semis of the ATP World Tour Finals when he faces Tomas Berdych on Friday, requiring just a set to confirm his place. In the earlier round-robin matches, the Spaniard beat Andy Roddick and Novak Djokovic to go top of Group A.

Nadal faces elimination only if he loses in straight sets to Berdych while Djokovic defeats Roddick in three sets.

Nadal holds an 8-3 record against Berdych, the last one being a victory in the Wimbledon final in July. However, he is not taking anything for granted.

I won two important matches in the round-robin but I am not qualified, said Nadal. I could meet with no-one in the semi-finals, I could meet with the island of Mallorca in the semi-finals and I could meet with Federer or everyone in the other group.

I have to think the minimum is to win a set to be in the semi-final, so it's not going to be easy against Tomas.

Berdych could prove to be tough proposition after he broke his slump in form with a win against Roddick during the second match of the round-robin stage on Wednesday.

He said, I think for me that's the best schedule for this week, to play maybe the last match of the season against the world number one, or if I can do well then to beat the number one and have a chance to play more in this tournament.

Novak Djokovic performed impressively against Nadal during round two on Wednesday, before complications with his contact lens ruined his chances. He will take on Roddick who still has an outside chance of qualifying.

The fact and the truth was that I was feeling great on the court, said Djokovic. I had time to prepare for this tournament mentally, physically. I put all my effort into it, desire to win, then you get on the court and this thing happens to your eye.

On Roddick he said, He's a huge server. He played great against Nadal. The group is still open.

On Thursday, Roger Federer and made it to the semis with straight set victories over Robin Soderling and David Ferrer respectively, in the last round-robin matches of Group B.

World No. 2 Roger Federer was the winner of the group after downing Sweden's Robin Soderling 7-6 (7-5) 6-3 in Thursday's early game before Britain's Andy Murray 6-2, 6-2 to join Federer in the semis.

Federer's victory was his third consecutive one in the group stages. It improved his record against Soderling to 15-1, the loss coming earlier this year in the French open quarter-finals.

The World No. 2 said, He (Soderling) always brings out something different every time he plays me, because he has to try different things. I was able to handle it well, which was a very happy feeling for me to have.

After a hard-fought first set, which Federer won 7-5 in the tie-breaker, the Swiss broke Soderling in the second set for a 5-3 lead with a sweet backhand that Soderling could only return into the net.

With Federer winning, Murray only had to win a set to confirm his place in the Semis. As it panned out, he took the match convincingly with a 6-2 6-2 win to go second place in group B.