Exceptions:-
U.S.A.R.F.U. VariationThe replacement of no more than six players on account of injury is permitted throughout the match, provided that any player who has been replaced on account of injury must not resume playing in that match.
Instruction from the I.R.F.B.
A player who is suffering definite concussion should not
participate in any match or training session for a period of
at least three weeks from the time of injury, and then only
subject to being cleared by a proper neurological examination.
U.S.A.R.F.U. Directive
Note:-