LONDON—Roger Federer, who will face Rafael Nadal in the semifinals of the ATP World Tour Finals, says he isn’t feeling a lot of pressure and may be able to play more freely against the Spaniard. Federer is 5-13 against Nadal since the beginning of 2008, but has won both of their meetings at the O2 Arena in London, where the event is staged.

“I see the light at the end of the tunnel,” Federer said. “There’s two more matches and that’s it. I just have to have the right mindset to give it one last go, maybe play with a little less pressure than I have in previous matches maybe with him. 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 kind of 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.”

Federer, who has won this tournament six times but is experiencing his worst year since 2002, said he didn’t come into the event with high expectations.

“Clearly the goal is always to win every tournament,” he said. “But I think I had to be slightly more realistic in recent weeks and months. I knew that sometimes just getting a few rounds into the bag was positive…I don’t know if the goal was necessarily for me to try to win this event right off the first match. I knew I had so much work to do with Djokovic in the first round, having played Basel and Paris. I was curious to see how I was going to adapt, how everybody was going to adapt, to the London conditions. For that reason I’m very pleased now.”