For a start Di Maria is Argentinian. Anyway he's been capped 57 times by Argentina, scoring 11 international goals and played 124 games for that small club called Real Madrid, scoring 22 goals.
Ramires capped 51 times by Brazil and was deemed good enough to play for that small club called Benfica.
Luis has been capped just 10 times for Brazil but managed to play 127 times for that small club called Athletico Madrid.
As for Raphael, Man Utd signed him as an 18 year old.
So I think most (the first 3 I mentioned at any rate) are talented enough to play in England.
Someone, somewhere has to put some sort of rules down as to who should be allowed a work permit/visa, otherwise any Tom, Dick or Harry would be able to come in, whether they were good enough or not.