The top sides field many overseas players because they think they are better than most home-grown ones. The fact that the England football team has done badly has much more to do with poor management and coaching than the large number of foreigners in the Premier League. It also is an indictment on the school programs in place and youth football as a whole. It has little to do with a lack of opportunity at club-level, for clubs will always look locally for cheap, ready-made talent. They are forced to look overseas because foreign-born players are proving to be better bets. Furthermore, these foreigners thereafter assist the few local-born players who have made the grade. Therefore, if you removed some of the best foreigners and replaced them with less good local players, it will actually weaken both club football and the national team.