The following additional players (maximum two per team) and replacement front row forward (maximum one per team) were nominated for registration with ERC by their clubs by 19 March, 2004, for participation in the knock-out stages:
BIARRITZ OLYMPIQUE: Mathieu Maillard, Chris Bentley
EDINBURGH RUGBY: Malcolm Clapperton, Craig Harrison
GLOUCESTER: Delarey du Preez, Riaan van der Bergh
LLANELLI SCARLETS: Richard Rees
LONDON WASPS: John Hart, Michael Roberts and Henry Nwome replacing Phil Greening
MUNSTER: Alan Quinlan, Michael Prendergast and Ross Callaghan replacing Eugene McGovern (nb - Former All Black star fullback Christian Cullen may make his debut in the quarter-final. Although registered at the start of the season, Cullen did not play during the Pool Stage because of a shoulder injury)
STADE FRANCAIS PARIS: Julien Rivier, Regis Sigoire
TOULOUSE: Arnaud Mathet, Julian Patey