So why exactly is Yammy so weak? He's the 0 espada and called the Ulquiorra and the other Espada nothing but trash. If they're trash compared to him, why is Kenny, who had difficulty with Nnoitra, just lopping off pieces of him without any effort. And as we saw at the end of the chapter, Kenny and Byakuya just pwned him to the face like it was nothing.
What was the point of making him the 0 espada if he was going to be so weak?