In Spain, as far as we can see, players are allowed to change numbers during the mid-season break. In 2004-05, Henrik Larsson switched from 17 to 7 when the previous incumbent, Javier Saviola, joined Monaco. A year later, Lionel Messi would swap his number 30 for 19, though of course his destiny as number 10 wasn’t too far away.
Messi had to continue to wear 30 in Europe that season, however, as UEFA’s rules are far stricter. So strict are they, in fact, that no number can be used more than once in the same season. This meant that when Andy Carroll joined Liverpool in 2011, he had to wear number 29 in the Europa League, despite the fact that he had inherited the number 9 from Fernando Torres domestically.
Back to mid-season changes, though – in the the Premier League handbook, section M4 states that:
While he remains with the Club a Player will retain his shirt number throughout the Season
for which it was allocated.
By and large, this has unsurprisingly been the case (we do have a fuzzy memory at the back of our heads though that Chris Sutton began 1996-97 wearing 16 for Blackburn before realising Alan Shearer had left and then changing to 9), but Aston Villa in 2010-11 are a massive exception.
No fewer than four players finished the season wearing different numbers than those with which they began it:
Player Old Number New Number
Moustapha Salifou 17 37
Andreas Weimann 42 26
Barry Bannan 46 25
Ciarán Clark 47 21
Why were they allowed to do so, and in such relatively high numbers, when the practice would seem to be outlawed, and why are there seemingly no other examples? Please get in touch if you know.