Swiss legend Roger Federer qualified first for the semifinals at the ATP World Tour Finals after thrashing Rafael Nadal from Spain 6-3, 6-0 on Tuesday.

Roger Federer of switzerland celebrates winning a point during the round robin singles tennis match against Rafael Nadal of Spain at the?ATP World Tour Finals at O2 arena in London, Nov. 22, 2011. [CFP]

The 30-year-old Federer took no mercy towards his biggest rival in career, smashing the world No. 2 in style.

It's the first time that neither player is ranked No.1 while the defending champion Federer is ranked No. 4 at the moment.

"It's a great match for me basically from start to finish," said Federer, who opened the match with a double faults, but managed to break in the sixth game to take the first set.

"I was able to do what I was hopping to do: dominate from the baseline, play close to the baseline, serve well, take his time away."

The 16-time Grand Slam champion then dominated the second set, breaking three times, then hitting his sixth ACE in the match to find two match points.

When Nadal returned the ball outside, the crowd cheered aloud for an amazing Federer.

"It's definitely one of the nice ones (wins), that's clear," said Federer who lost to the 25-year-old Nadal 17 times in their previous 25 meetings.

"I had some good ones in my career, my lifetime. This one ranks high because it's against my biggest rival probably. It's World Tour Finals, where it really matters. That I've been able to come through so convincing is a little bit of a surprise to me, but it ranks extremely high."