Why is Kei Igawa so bad...smart fans only?

Where I live I don't get any Yankee games...and I really pay more attention to National League games, teams, and players. I was just wondering what Kei Igawa's problem has been this season. I remember Posada and Giambi hyping him up calling him the best pitcher in camp, and the next Roger Clemens. But I seen on yahoo sports that Hughes woud replace him in the rotation and it's no wonder looking at his numbers. Velocity problems? Command problems? Was he overhyped? I'm just wondering.