Roger Federer produced a virtuoso performance to defeat Janko Tipsarevic in straight sets and give his ATP World Tour Finals campaign the best possible start in London.
The 17-time major champion overwhelmed an only half-fit Tipsarevic 6-3 6-1 at the O2 Arena as he chases a seventh end-of-season title in 12 years.
Tipsarevic meanwhile, goes into his final two round robin matches against Juan Martin Del Potro and David Ferrer knowing he has little margin for error should he wish to qualify for the semi-final.
Federer stormed to a dominating win over Tipsarevic.
"I'm very happy to be playing so well. It's a great feel here and a great atmosphere," Federer said.
Federer, victor in the last two events in the English capital and reigning Wimbledon champion went into the tournament having lost his world No.1 ranking to Novak Djokovic and downplayed as a potential winner in 2012 amid the encouraging form of Andy Murray.
But having been drawn in the more favorable of the two groups for the round-robin stage, the Swiss' route into the traditional knockout phase looks like all but a forgone conclusion.
Facing a man in Tipsarevic, the beneficiary of Rafael Nadal's withdrawal through injury, who had never defeated Federer in their previous five meetings, the Serbian was confronted with a tough task to break down the second seed's rearguard.
Breaking early in the first set, Federer was able to control from the baseline, occasionally mixing up his ground strokes as though to portray a man merely warming up for greater tests.
The 28-year-old Tipsarevic, from Belgrade, who has risen from 49th in the rankings into the world's top nine inside a year and sustained it through 2012, was forced to chase the match after losing his dominating serve first up.
While no thrills accompanied the end of the first set, the second saw Federer further endear himself to a crowd, who would be hard-pressed should they be forced to chose between him and home-favorite Murray.
Teasing drop shots were coupled with solid baseline hitting, as Federer nullified the power of Tipsarevic and allowed him to open up two breaks in the second and final set, to wrap it up in 68 minutes, and a timely reminder for Djokovic and Co. that he is far from willing to give up his title.
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