By NBF News

Roger Federer maintained his 100% record at this year's ATP World Tour Finals and secured a semi-final spot with a straight-sets win over Robin Soderling.

The world number two made sure that his qualification from the round-robin stage would not depend on complicated mathematics as he despatched the Swede 7-6 (7-5) 6-3 at London's O2 Arena.

Federer tops Group B as a result of the victory, and Britain's Andy Murray will join him in the last four if he takes a set off David Ferrer in Thursday's late match at 2000 GMT.

The nature of the round-robin system meant that there were 10 different qualification scenarios going into the final two Group B matches, with the possibility that the percentage of sets or games won could come into play.    606: DEBATE

Who are you tipping to twin the ATP World Tour finals

However, with two wins behind him Federer knew that a third successive victory at the O2 was the best way to guarantee progress, and the Swiss achieved it in ruthless fashion.

Federer went into the match with an overwhelming 14-1 record in previous encounters with Soderling, and having done much to erase the memory of that lone defeat – in this year's Roland Garros quarter-finals – by responding with thumping wins over the Swede at the US Open and in Shanghai.

The 16-time Grand Slam champion looked as unruffled as ever in the early stages, securing an early break with a dipping backhand that Soderling could not control at the net and apparently cruising towards the opening set.

It therefore came as quite a shock to see the 29-year-old make successive forehand errors at 4-3, 30-30, and so allow Soderling back into the set to eventually force a tie-break.

Federer pleased to beat in-form Soderling
Federer looked to have made the decisive move with a series of punishing forehands to break for 3-2 followed by two aces in a row, but Soderling got the mini-break back, only to leave a floating Federer backhand on set point that dropped agonisingly inside the line.

“It's the worst feeling in the world when you leave a shot like that, you have a split second to decide, and then see it go in,” said Federer of the lob.

Soderling added: “I think he mishit it a little bit, so at first I was pretty sure it was going go out, and then as soon as I let it go I thought it was going a lot closer to the line than I expected.

“Of course, it went in, so it was a little bit unlucky but it was my fault. Against Roger you need to have the luck to win. I'm not saying I would have won but I was a little bit unlucky today.”    Against Roger you need to have the luck to win. I'm not saying I would have won but I was a little bit unlucky today

Robin Soderling
There was more torment for the 26-year-old Swede at the start of the second when he fashioned another two break points, only for a heavy forehand down the line on the second to be ruled a fraction wide by Hawkeye.

Up until that point Federer had made relatively little headway on the Soderling serve but, after two break points went begging in game four, the Swiss made the breakthrough in game eight with a beautiful forehand winner and another vicious backhand that left his opponent flat-footed at the net.

The world number two was in full flow now, wrapping up the win with a majestic service game to complete a hugely satisfactory opening five days at the O2.

“To play against Robin is never easy. He's a big hitter and you have to work on your defence,” added Federer.

“He can be very frustrating to play against, but I took it to Robin and I'm very pleased to have won.”

He added: “I could still have maybe needed some time to wait for the Murray match tonight, so I just wanted to come out and try to play as good a match as I can because losing is never the solution to trying to win a tournament.

“That's why I'm happy that all three matches were straight sets, I didn't waste any energy, I'm playing real well and I'm through to the semis so it's all good right now.”