Winning a tennis match at a high level is extremely impressive; playing fifty-something matches while only suffering two losses borders on supernatural absurdity.
After winning 43 consecutive matches—including multiple wins over Roger Federer and Rafael Nadal—Novak Djokovic's ridiculous streak was snapped at Roland Garros. Despite that loss, he continued to massacre everybody that got in his way.
His several wins include the Australian Open, Wimbledon and seven other tournaments, in which he beat many highly ranked players.
In 2010, he was not really considered a major grand slam contender. His serve was a liability—last year he had more double faults than aces—he was not consistent at all and he was prone to breathlessness and tiredness as the drop of a hat.
However, going into 2011, Djokovic obviously worked like a dog, got his confidence up and most importantly, went on a gluten-free diet (which helped the tiredness). He has now started pounding the ball off of both flanks, serving like a monster, volleying very well and moving well.
This has taken his game to the next level; he is virtually unstoppable and there are no evident weaknesses in his game.
Going into the US Open, which players outside of the top five have the biggest chance of beating the Serb?