Bradford-bound second-rower Frank Winterstein was one of the players they wanted to replace – the former Widnes man tore a pectoral muscle in the 42-24 defeat to New Zealand on the opening weekend of the tournament.
Competition rules state that requested changes to the 24-man squads which are made after 21 October are at the discretion of tournament organisers and will only be granted in exceptional circumstances.
A statement said: “Samoa recently approached RLWC2013 to change two players in their squad. After due consideration, the request was denied.”
It means that coach Matt Parish has only been able to name an 18-man squad for their clash with Papua New Guinea in Hull tonight.
Prior to the tournament, Samoa had named a 26-man squad, only to be told by tournament organisers that it must be reduced to 24.
They then fielded a total of 25 players in the warm-up game against England Knights at Salford a week before the tournament.
Australia coach Tim Sheens hinted on Saturday that he may try and call up a replacement for Luke Lewis, who was ruled out of the World Cup with a dislocated shoulder, suffered during the win over Fiji, but admitted he wasn’t sure whether the competition rules would allow.