i think you miss the point,folk look at youngsters or highly rated players going to man u and think that will equate to definite success, Ferguson has made some signings that people thought would be sensational and turned out to be flops,i am trying to get over that he is not some sort of god, manure do produce flops as well
oh and of the genuine players you mentioned there-
Cantona, Keane, Rooney, Cole, Sheringham, York, Bruce, Pallister,Nav Der Sar + Ferdinand were all already established players in England and was much less a risk