A player who has been sent off before the kick-off may be replaced only by one of the named substitutes.
A named substitute who has been sent off, either before the kick-off or after play has started, may not be replaced.
My question: If no substitutes have been named and a player is sent off before play has begun, may the affected team complete the side with a player who subsequently arrives?
The “strange” answers by FIFA:
Q&A 2004: The team may be completed with this player provided this is allowed by the rules of the competition.
Q&A 2006: Yes
I don’t understand. Can you explain how is it possible to replace this player?
USSF answer (February 26, 2008):
The world of FIFA is wonderful and strange, and sometimes a bit confusing. In this case, the answer is yes, if the rules of the competition provide for it. If they do not, then no player may join the game if he (or she) arrives after the match has begun. It might have been better if, in 2004, the IFAB (not necessarily FIFA) had answered the question by saying, “No, unless this is permitted by the rules of the competition.” That would also help explain the omission of any qualifiers in the 2006 version of the Q&A.