Roof makes Wimbledon a lottery: Fed ROGER Federer believes the roof on Wimbledon's famed Centre Court has made a lottery out of the pursuit of the championship title. The great Swiss, chasing Pete Sampras's record of seven titles, survived an epic battle to defeat France's Julien Benneteau on Friday to reach the last 16. But he had been just two points from defeat in the fourth set before clinching a 4-6 6-7 (3-7) 6-2 7-6 (8-6) 6-1 win and avoid slumping to his earliest defeat at the All England Club in 10 years. Federer's struggle was played out under the roof, as was the final set of Rafael Nadal's historic loss to Czech world No.100 Lukas Rosol in the second round 24 hours earlier. Even defending champion and top seed Novak Djokovic struggled in the hothouse conditions, dropping the first set to veteran Czech Radek Stepanek before reaching the last 16 in four sets. "It does play different indoors. Obviously that's a bit of getting used to. Indoor grass not something we're quite familiar with," said Federer after pulling off his eight career recovery from two sets to love down. "You just don't have the elements. You just don't have the sun setting, which can be tricky at times. From the one end it's easier; from the other end it's tough. You have the wind swirling. When I was warming up I was thinking that's going to be a big factor for the players out on Centre Court if they're going to leave the roof open or not. "Don't know if it would've favoured me or not even more so, but it changes everything. So then does it play slower indoors? I would think so, a little bit, right? "But then at the same time, you can really play yourself into a trance-like state like I thought Rosol was in in the end of the fifth. That's harder to do outdoors with the elements." Federer believes that the unique conditions served up under the roof can cause more shocks in the sport and keep the top three players in the world on their toes. "This is not against Rafa, but it was nice to see it's still possible," said Federer. "I think 15 years ago you had matches like this so much more often on the faster surfaces, that a guy could catch fire and just run through you. "Today it's virtually impossible because you make so many more returns and conditions are so much slower with the elements. "In the fifth set it was just a joke. I was laughing because of his performance for 10 minutes after that. I couldn't believe that he pulled it off the way he did." Federer's next date is against unseeded Belgian Xavier Malisse for a place in the quarter-finals. Malisse pushed Federer to five sets in the second round in 2001.