18.07 As a rule, a player may not play in a UEFA club competition (i.e. UEFA Champions League and UEFA Europa League, but not UEFA Super Cup) for more than one club in the course of the same season. Exceptionally, however a player who has been fielded in the first, second, third qualifying round or the play-offs of the UEFA Champions League or UEFA Europa League is entitled to play in the UEFA Champions League or UEFA Europa League for another club as from the group stage. Moreover, as from the start of the round of 16, a player can be registered in accordance with paragraphs 18.18 to
18.21 below. A substitute player who has not been fielded is entitled to play for another club competing in the UEFA Champions League or UEFA Europa League in the course of the same season, provided that he is registered with the UEFA administration in accordance with the present regulations.
Subsequent registration
18.18 For all matches from the start of the round of 16, a club may register a maximum of three new eligible players for the remaining matches in the current competition. Such registration must be completed by 3 February 2014 (24.00 CET) at the latest. This deadline cannot be extended.
18.19 One player from the above quota of three who has been fielded in a UEFA club competition group stage match for another club in the current season may exceptionally be registered, provided that the player has not been fielded:
a) in the same competition for another club; or
b) for another club that is currently in the same competition.
18.20 One or more players from the above quota of three who have been fielded only in the first, second or third qualifying round or play-offs of the UEFA
Champions League or UEFA Europa League for another club are entitled to e registered.
18.21 If the registration of such new players causes the number of players on List A to exceed 25, the club must remove the necessary number of currently registered players to reduce the squad to 25 players again. The quota of the “locally trained players” must be respected when registering new players. Newly registered players must wear set numbers which have not yet been assigned.