If he is a non-EU citizen then the home office are not obliged to allow him to get into the country in order to work.
Their rather loose rule states that in order for a non-EU footballer to be eligible for a work permit:
[*:308de804e5]a player must have played for his country in at least 75% of its competitive 'A' team matches he was available for selection, during the two years preceding the date of the application; and
[*:308de804e5]the player's country must be at or above 70th place in the official FIFA world rankings when averaged over the two years preceding the date of the application.
The main exception is where an outstanding youngster is involved - one who couldn't feasibly have gained the necessary experience during his career to date. How they come to the conclusion the youngster is outstanding TENDS to depend on which club is asking for the permit. If you're top 4 you're quids in. If you're not, then you're probably not.
The full text is here and is based on the 08/09 season but it has not changed much, if at all, since then.
Bloody hell the home office must have been really busy over the past few years with all the influx of foreign workwers into the country??