Why the **** do you even talk about Kaka' as if there is even the possibility of him coming to your club, you should be glad that Chelsea still doesn't look like Madrid, Real is the most repulsive club in the world with their poaching of the best players from the biggest clubs, you should be glad that Chelsea's not like that.
Taking a superstar and a symbol of some club is the worst thing in football, first you brake the hearts of the fans of the clubs who's star you're stealing.
Second he'll never feel like your's and you'll never have that feeling when he plays that he for example is Chelsea, that those colors run in his blood. And he'll never give his all to the new club, (unlike whores of players like Ibrahimovic or Ronaldo) it's the same as love if you loved once with your whole heart than you can't love someone else like that anymore.
And the third thing is expectation, for example Barcelona's fans except the same from Henry like what he played at Arsenal and won't settle for less, and players only drop from a certain point in their career so that's never going to repeat to the same extent (ok not definetly, but be realistic), but if he'd stayed at Arsenal they would appreciate him for all that he's done and understand a little drop in form due to age, he would still be a legend.
I cannot imagine players like Gerrard, Totti, Del Piero, Maldini or Raul leaving their clubs and that would be a catastrophe in my eyes, and yes i count Kaka' in with these players because Milan have found him when he was a kid, believed in him and he's shined at our club, the same i think for Messi in whom Barca have put a lot, and helped him with his growth condition when he was a kid, it's a shame for Ronaldinho though, eventhough i'm a Milan fan and he might end up here, and i think that he's one of the best talents to have ever played football, i would have still liked it more if he stayed and if Barca's fans would appreciate a man who almost single-handedly ressurected their club, it wouldn't surprise me if he's stopped working so hard because of his disappointment in how fast the people forgot what he gave to them.