J'ai trouvé la réponse :
http://www.games-workshop.com/MEDIA_CustomProductCatalog/m780049a_Blood_Bowl_Competition_Rules.pdf
Pass Block (General) A player with this skill is allowed to move up to three squares when the opposing coach announces that one of his players is going to pass the ball (but not a bomb). The opposing coach may not change his mind about passing once Pass Block's use is declared. The move is made out of sequence, after the range has been measured, but before any interception attempts have been made. A player may not make the move unless able to reach a legal destination and may not follow a route that would not allow them to reach a legal destination. A legal destination puts the player in a position to attempt an interception, an empty square that is the target of the pass, or with his tackle zone on the thrower or catcher. The player may not stop moving until he has reached a legal destination, has been held fast by Tentacles or has been Knocked Down. The special move is free, and in no way affects the player’s ability to move in a subsequent action. The move is made using all of the normal rules and skills (for example, having to dodge in order to leave opposing players’ tackle zones.)
Players with Pass Block may use this skill against a Dump Off pass. If a player performing a Pass Block in their own turn is Knocked Down then this is a turnover, no other players may perform Pass Block moves, and your turn ends as soon as the results of the pass and the block are resolved.