Off cource we should look into the present, but still, he only did good for 1 year. I feel that that fact is enough to be at juve. If he does well another year (or 2) than it's different, but at the moment not.
There are a lot of players who have done well last season, but that doesn't mean they are good enough for us. Ok, Nani get's a 25 mio transfer to Man utd, but I couls easily see him back fire. There are no garantees after 1 year, that's all, and that is what we need at the moment