MELBOURNE - Switzerland's Stanislas Wawrinka claimed his first Grand Slam title in dramatic fashion on Sunday when he upset injury-troubled world number one Rafael Nadal in the Australian Open final. The eighth seed roared through the first two sets and overcame the distraction of a back injury to Nadal, and then the loss of the third set, to take it 6-3, 6-2, 3-6, 6-3 in two hours 21 minutes.Nadal, who was chasing his 14th major title, looked as if he might pull out with the back injury but he fought back to take the third set and force the match into a fourth set. It was a stunning result for Wawrinka, who had never taken a set off Nadal in their 12 previous meetings and won his first Slam title at his 36th attempt, the second longest wait on record. "For me it's the best Grand Slam ever. I'm enjoying very much to play here," Wawrinka said, who lost in five sets to Novak Djokovic in last year's fourth round. "In one year a lot has happened. Right now I still don't know if I'm dreaming or not. We'll see tomorrow morning."Wawrinka's win was a rare shock at the top of men's tennis after several years of dominance by the game's top four players. The last outsider to win was Juan Martin del Potro at the 2009 US Open. Injury-prone Nadal was in tears as he said: "Many thanks Stan, you really deserved it, I'm very happy for you. I had bad luck against you today but you really deserve it." Nadal has had injury problems in the past in Melbourne. He missed the 2006 and 2013 editions, had to retire injured in 2010 and was hit by a muscle strain during his 2011 defeat to David Ferrer."My team, I tried hard, thank you very much. Without them it would be impossible to be where I am today. Sorry to finish this way, I tried very, very hard," said the devastated Nadal. "This year is one of the more emotional tournaments of my career." Wawrinka, who also shocked world number two Djokovic in the quarter-finals, became the first man to defeat the top two seeds at a Grand Slam since Sergi Bruguera at the 1993 French Open. Despite playing his first major final, he began nervelessly and after holding his opening two service games he made the first move, breaking Nadal in the fourth game. The Swiss again had a break point in Nadal's next service game as he held his own serves without undue pressure. But he was three break points down serving out for his first ever set against Nadal, only to win the next five points with some magnificent serves to go one set up in 37 minutes.Fresh from the psychological breakthrough, Wawrinka broke Nadal to love in the opening game of the second with a cracking backhand return winner. The Swiss was in the zone, reeling off 12 consecutive points against the nonplussed Nadal, who received a time violation warning for taking too long between points. Nadal's problems mounted when he grabbed his back after playing a forehand. He called for the trainer at the next changeover and went off the court for a medical timeout at 2-1 in the second set. Wawrinka argued with the chair umpire about why he wasn't told what Nadal's injury was, as the crowd became restless with the Spaniard's seven-minute absence. When Nadal re-emerged he looked distressed and lost his serve for a third time as Wawrinka charged to a 4-1 lead. The Spaniard sat with his head in hands at the changeover. Wawrinka served out for the second set as Nadal disconsolately walked to his chair and received further courtside treatment on his back.However, Nadal fought back and broke Wawrinka's serve for the first time early in the third set. And as the treatment or possible painkillers took effect, he soon led 4-1 against the unsettled Swiss. Wawrinka had a couple of break points in the ninth game but Nadal served out for the third set to take the final into a fourth set, as an amazing revival suddenly looked on the cards. Wawrinka missed two break points early in the fourth set but he got his fourth break of the night with a big forehand winner to take a 4-2 lead and move within sight of the championship. Nadal broke back but Wawrinka broke yet again, and he served it out authoritatively, winning the title with a forehand and raising his arms aloft in celebration.