Belgium keeper Casteels fails in fitness bid
The 21-year-old goalkeeper sustained the injury while playing for Hoffenheim in a 1-1 draw with Hertha Berlin in April, but was named in Belgium's 23-man party when the list was submitted to FIFA on Monday.
However, further tests have shown he is not fit enough to participate for Marc Wilmots' men, and he has since been replaced by Bossut of Zulte-Waregem.
Though Belgium had submitted their final list, FIFA rules allow injured players to be replaced up to 24 hours before a team's first World Cup match.
Bossut will travel to Brazil as third-choice behind Chelsea's Thibaut Courtois and Simon Mignolet of Liverpool.
Anderlecht's Silvio Proto had been on the provisional list ahead of Bossut, but he is also injured.
Bossut made his international bow in Belgium's 5-1 friendly over Luxembourg on May 26.
There are no other changes from Belgium's provisional squad. Aston Villa striker Christian Benteke was ruled out of the tournament with an Achilles injury, while Radja Nainggolan of Roma was a notable absentee.
Squad in full:
Goalkeepers: Sammy Bossut (Zulte-Waregem), Thibaut Courtois (Atletico Madrid), Simon Mignolet (Liverpool),
Defenders: Toby Alderweireld (Atletico Madrid), Laurent Ciman (Standard Liege), Vincent Kompany (Manchester City), Nicolas Lombaerts (Zenit), Daniel Van Buyten (Bayern Munich), Anthony Vanden Borre (Anderlecht), Thomas Vermaelen (Arsenal), Jan Vertonghen (Tottenham)
Midfielders: Kevin De Bruyne (Wolfsburg), Nacer Chadli (Tottenham), Steven Defour (Porto), Moussa Dembele (Tottenham), Marouane Fellaini (Manchester United), Eden Hazard (Chelsea), Adnan Januzaj (Manchester United), Dries Mertens (Napoli), Kevin Mirallas (Everton), Axel Witsel (Zenit),
Forwards: Romelu Lukaku (Chelsea), Divock Origi (Lille)