He is consistently getting beat by players outside the top 10 now, and is routinely losing to nearly everyone inside the top 5. In fact, his two wins posted over Federer this season are essentially hollow because he caught Federer in the biggest funk of his career. And still, Federer had chances to win both matches.
In fact, he got some of the most spectacularly easy slam draws a player could ask for, and in consecutive years too. How he managed to get those draws is absolutely beyond me, but he is simply not a top 5 player. In fact, he has far more points to defend than either Roddick or Del Potro due to his TMC + HC points, and unless he picks up the pace, he's going to drop like a rock come the end of the year.