The Referees Committee appoints the referee team for each match. Only referees whose names appear on the official FIFA list of referees are eligible. The Referees Committee’s decision is final.
UEFA arranges for the referee team to arrive at the venue the day before the match. If a member of the referee team does not arrive at the venue by the evening before the match, UEFA informs the clubs immediately. The Referees Committee takes the appropriate decisions, which are final.
If a referee, assistant referee or video assistant referee becomes unfit to officiate or is otherwise incapacitated before or during a match, he is replaced by another member of the referee team as follows, in accordance with the IFAB Laws of the Game:
The referee is replaced by the fourth official or the video assistant referee if one has been appointed and is available on-site, or by an assistant referee.
An assistant referee is replaced by the fourth official or by the reserve assistant referee if one has been appointed.
A video assistant referee is replaced by the assistant video assistant referee (if certified as video assistant referee) or by the referee if he is unfit to referee but able and certified to serve as video assistant referee.
If necessary, the match will take place without video assistant referees and/or without a fourth official.