LONDON - US Open champion Andy Murray withstood an early onslaught to beat Tomas Berdych in his first match on home soil since winning his maiden grand slam title and Novak Djokovic overcame Jo-Wilfried Tsonga as the ATP World Tour Finals began on Monday.Murray, greeted on court at the cavernous O2 Arena in London like a returning hero less than two months after beating Djokovic in Flushing Meadows epic to end Britain’s 76-year wait for a male grand slam winnner, wore down Berdych to win 3-6 6-3 6-4.World No 1 Djokovic also had to contend with some blistering firepower from free-wheeling Frenchman Tsonga before registering a 7-6 6-3 victory to move top of Group A.Djokovic and Murray will face each other in the latest installment of their rivalry on Wednesday (today) when the winner will take a huge stride towards the semifinals of the year-ender.Neither had it all their own way with Murray admitting he had struggled to deal with Berdych’s power. "Some of the time in the first set he just completely overpowered me,” Murray told reporters. Djokovic admitted he was second-best during the first set against Tsonga when he saved break points at 3-3 and 5-5 and never threatened the Frenchman’s delivery."To be honest, he was the better player throughout the first set,” Djokovic told reporters. "I managed to stay mentally tough and fight my way through.”Defending champion Roger Federer was due to begin his campaign on Tuesday against world No 9 Janko Tipsarevic, who qualified for the eight-man finale in the absence of the injured Rafael Nadal.