Roger Federer has revealed his joy at becoming the first player to book his spot in the semi-finals of the ATP World Tour Finals in London.

The world number two eased past David Ferrer in straight sets on Thursday and admits that it was a great achievement to end the Spaniard's recent run of good form.

"I'm extremely happy, it's a tough match. David's been on a great run, winning in Paris was so deserving," Federer told BBC Sport. "It was a long match and I'm extremely happy. I played a great match.

"You say I've qualified and I'm obviously relieved and thrilled that that's the case. Ferrer is so respected by the fellow competitors.

"I enjoy playing against him, not because of the 14-0 [head-to-head record] but because he's a great guy and a great competitor."

Federer plays his final group match against Juan Martin del Potro on Saturday.