LONDON (Reuters) - Swiss maestro Roger Federer will have an early chance to disprove the notion that Novak Djokovic is untouchable when they meet in their second round-robin match at the ATP World Tour Finals on Tuesday.
Federer outclassed Tomas Berdych 6-4 6-2 to kickstart his 14th consecutive appearance at the season-ender on Sunday, a few hours after world number one Djokovic had demolished Japan's world number eight Kei Nishikori 6-1 6-1.
Both already look odds on to take the top two spots in Stan Smith Group but Tuesday's 43rd meeting between the pair (both have won 21) looks set to decide who will advance to the semi-finals as group winner.
Djokovic has won his last 23 matches and has been unstoppable since he picked up his third grand slam of the year by beating Federer in the U.S. Open final.
Asked if the near 7,000-point gap between Djokovic and the rest in the ATP ranking points was proof of the Serb's invincibility, Federer was not convinced.
"That depends on who looks at the gap," Federer, who pulled out of last year's final against Djokovic with a back problem, said. "I don't think I'm that far off.
"Then again, let's speak in two days. Two days is not the match that I care the most about, to be quite honest.
"It's an important match, very important. But it's not the match. It's going to be interesting to see how I play that one. I'm curious to find out myself."
Federer knows he can ill afford the sloppy start he made against Berdych when two double faults gifted the Czech a 2-0 lead. After that, however, he barely put a foot wrong.
"It was not the best start. I have to clean that up clearly for the next match," he said.
Sunday's opening matches were reminiscent of many of the one-sided singles matches here last year, and Federer said the slowish court surface meant it was very difficult to turn around a match once you fall behind.
"Maybe it's the end of the season, maybe it's the surface, we saw the faster results here last year," he said.
"Seems like whoever takes charge of the baseline, and if you cannot serve your way out of trouble often enough, which is hard to do here because of the pace of the court, the guy from the baseline wins, the better one.
"That's why we see some crushing scores."
Reporting by Martyn Herman; editing by Justin Palmer/Greg Stutchbury