LONDON — Novak Djokovic said he will use his 22-match winning streak as a launchpad for an all-out assault on more Grand Slam titles next year. The Serb claimed the ATP World Tour Finals title for a third time Monday with an authoritative win over world No. 1 Rafa Nadal and believes he has taken his game to a new level since losing to the Spaniard in the US Open final. Throughout his career the 26-year-old has used setbacks as motivation to sharpen his game and the way he has steamrollered through the last two and a half months of the ATP season is ominous for Nadal, Andy Murray, Roger Federer and any other player with designs on the top silverware in 2014. His form is reminiscent of his incredible 43-match unbeaten streak in 2011 when he won three of the year's four majors — a run that was sparked by Serbia's Davis Cup triumph over France at the end of the previous year. Djokovic's first priority is to regain the Davis Cup for Serbia in this week's final against the Czech Republic, then after re-charging his batteries it will be all-systems go. “This can serve as a great platform for 2014 season,” Djokovic told reporters. “I'm extra motivated and inspired to work and get myself, first of all, rested and recovered in the off-season, and then work on my game and get ready for the Australian Open. “The only thing I'm not as satisfied about (this season) is the fact that I lost the three big matches in the three Grand Slams. The Grand Slams are the tournaments where I want to win, where I want to get my hands on the title. “That will be my highest priority for next year.” Djokovic lost to Nadal in an epic French Open semifinal, Murray in the Wimbledon final and Nadal again in the US Open final, and also lost his No. 1 ranking to the Spaniard in November. That defeat in New York was particularly tough to take and Djokovic has since worked on a more attacking style of play to go with his incredible defensive qualities. On Monday he volleyed superbly, giving his game a new dimension. “Maybe I didn't do that in US Open final as much as I should have,” he said. “In our last two matches, in finals of Beijing and here, I've done it pretty well. “I feel more comfortable on the net than I was last year, that's for sure.” Djokovic's rivalry with Nadal now stretches 39 matches and there have been periods of domination for both. Nadal won five in a row in 2008-09 and Djokovic won seven in succession in 2011, but the two players are so well-matched that Djokovic believes the balance of power will keep shifting. “It hasn't been the case that one player wins, you know, 10 in a row being very dominant because really goes up and down,” Djokovic said. “We push each other to the limit. We make each other better players. We make each other work harder, especially when we play against each other. It's always a huge challenge.” Spanish duo upset Bryan brothers American duo Bob and Mike Bryan's incredible year ended in disappointment when they were beaten by Spain's Fernando Verdasco and David Marrero in the ATP Tour Finals doubles final Monday. Verdasco and Marrero, the sixth seeds, upset the favorites 7-5, 6-7 (3), 10-7 as the title went to a Spanish pair for the second successive year following the triumph of Marcel Granollers and Mark Lopez 12 months ago. The Californian Bryan twins were looking to win their 12th title of 2013 and surpass the 11 they won in 2007 and 2010, but the world's top-ranked pair were edged out in a match tiebreak. — Agencies