#4 Jason Day
The Australian recently gave up the title of the No.1 golfer in the world and his back troubles in the last few months have hindered his chances at a lot of key events. Having said that, Jason Day possesses one of the most powerful swings in golf. He creates immense power through rotation of his torso - back and forth during the swing. He does a phenomenal job of creating speed while keeping his backswing compact.
Again, like Rose, he gets in to a really strong position at the top and is able to free wheel it from there owing to his lower body and core stability. Jason works hard on his fitness in the gym so that he can keep making those high speed swings without injury.
Jason has a very quite head and a great athletic posture during his swing which are great qualities. To go along, he makes minimal lateral body shift through the transition. Those qualities are what make him a contender in most of the events he plays.