Because there are no more excuses according to him. He said he feels great. He says his swing is clicking. He says he is ready.
But what else would anybody expect him to say: "My knee still hurst a little, my off-course problems are still in my head, my swing is just not there yet..." He is always very positive before a tournament he enters. All players should be. It'll be interesting to hear what he has to say come Sunday night (or before if he doesn't finish).