Novak Djokovic made a commanding start at the ATP Finals, beating second seed Stefanos Tsitsipas in straight sets 6-4, 7-6.The Serbian is going for record-equalling sixth Nitto ATP Finals title, which would make him even with Roger Federer, and he was ruthless from the off, breaking the young Greek in the first game.“The first game was very important to break his serve,” Djokovic said. “Starting with a break of serve is obviously a huge boost in confidence and a relief as well because we both knew it would be a tight match.”Tsitsipas came into the match with …