ATP World Tour Finals: Roger Federer looking forward to facing Rafael Nadal
Roger Federer hopes being the underdog can play to his advantage when he meets Rafael Nadal at the 02 on Sunday.
Last Updated: 11/11/13 5:46am
The six-time champion fought back from a break down in the second and third sets to win 4-6 7-6 (7/2) 7-5 against Juan Martin Del Potro to set up a meeting with the world No 1.
History certainly favours the Spaniard, who leads their head-to-head 21-10 and has won 13 of their last 17 matches, including all three this year.
While Federer has endured his worst season for more than a decade, Nadal has returned from serious injury to win 10 titles and reclaim the number one ranking.
The main source of encouragement for Federer is that he was won all four of their previous matches indoors, including both times they have met at the O2.
Federer said: "I just feel like I need to look at it more as being an underdog a little bit because of circumstances, because of my year, because of his year. Maybe that free swinging is what I need to do a little bit more tomorrow.
"We know each other that well. He's going to do exactly what he needs to do, I'm going to try to do what I need to do. Hopefully it's going to match up good for me. If not, he deserves it. He's had a wonderful season."
For most of the clash with Del Potro it looked like it would be the Argentinian who would be going through to meet Nadal.
Asked how he felt at 3-0 down in the decider, Federer said: "I fought back the whole match. I was thinking, 'Here we go again'.
"I was really getting angry at myself, how could I play a loose game, why is this happening?
"Because of the last few weeks probably I stayed relatively calm inside because I had a lot of ups and downs throughout the matches in Basel and in Paris, then again here.
"I wasn't in many of Juan Martin's service games so I felt like probably I would get one more chance to break back. It's exactly what happened. Once on even terms, I was able to play a little bit more freely.
"It was a great finish. I was very happy. To get the victory was a great feeling."
Del Potro is the only player other than Federer, Nadal, Novak Djokovic and Andy Murray to win a grand slam in the last 35 tournaments, and many within tennis believe he will be the one to break their stranglehold again.
The Argentinian was frustrated he could not take his chances against Federer, but said: "I think I had a great season.
"For this year my goal was to try to play at the same level as the top guys. I am the only player who beat all of them this season, which means something for me."
Sunday's other semi-final pits defending champion Novak Djokovic against Stanislas Wawrinka, who will be looking to end a 13-match losing streak against the Serbian.
The pair have played two of the best matches of the season, with Djokovic winning five-setters at the Australian and US Opens.
Wawrinka has made the last four on his debut, and Federer said of his countryman: "I don't know if I'm more excited that I won or we're both in the semis. It's historic."