Valon Behrami will sit out Switzerland's friendly against Costa Rica on Tuesday night after getting a knock on his right ankle in training.
Behrami, who was part of the Swiss squad at the 2006 finals and also UEFA Euro 2008, took a blow to his ankle in the final practice session staged at the national-team training camp in Crans-Montana before the warm-up match in Sion.
Medical staff gave him the all-clear on Monday evening but he will not be risked against the Costa Ricans, officially listing his status for the match as "questionable".
Tuesday's match is only the second fixture between the two nations, with Switzerland scoring a 2-0 victory in Geneva in September 2006 in the only previous meeting.
The West Ham United midfielder is one of Ottmar Hitzfeld's key players for the finals, where the Swiss will meet Spain, Chile and Honduras in the group stage, even though he has not played for a month.
The 24-year-old had only returned to training a fortnight ago after a knee problem caused him to miss the final Barclays Premier League game of the season against Manchester City on 9 May.
Hitzfeld is believed to have settled on his starting XI for the World Cup, with No11 Behrami set to play in a wide midfield role, swapping flanks with Bayer 04 Leverkusen's Tranquillo Barnetta on a regular basis.
The German-born manager will also be without FC Lucerne midfielder Hakan Yakin and Hannover 96 defender Mario Eggimann against Costa Rica, but both are expected to be fit for the World Cup.
Switzerland have lost their last two home friendlies to Norway and Uruguay, meaning Hitzfeld is eager for a morale-boosting win ahead of their send-off match against World Cup holders Italy in Geneva on Saturday. It is a deliberately tough test, with the Swiss set to start their finals campaign on 16 June against European champions Spain in Durban