Of course he's going to lose sharpness. Training fitness is totally different to match fitness. It will also be an issue if the Phoenix do not allow him to train with them - doing your own training is never the same as training with a squad. (Does anyone know if it's definite that he is allowed to train with them)
As far as playing in the Indian league goes - the only comment I make is Kayne Vincent played in it and was a star, then he moves to Japan and hardly gets game time. So that's the quality of that league. So what if Colosimo, Mehmet are there, doesn't mean Indian League is great prep for AWs going to the world cup.
I guess he'll be fine if AWs are only going to be playing against nobody but the CONCACAF team they come up against will not exactly be pushovers.
