Valon Behrami suffered a suspected hamstring injury as Switzerland completed their FIFA 2010 World Cup preparations with a 1-1 draw with reigning champions Italy.
The West Ham United midfielder was replaced by winger Tranquillo Barnetta after 58 minutes of the warm-up friendly in Geneva, and his status will now be assessed ahead of Switzerland's Group H opener against Spain on 16 June.
Earlier, the 25-year-old had produced a lively display on his return to the side after missing last week's surprised defeat by Costa Rica with a slight ankle problem.
Gianluca Zambrotta had to make a heroic block to deny the midfielder a third international goal in 27 appearances on 16 minutes. By then Gokhan Inler's opening goal had already been cancelled out by Italy striker Fabio Quagliarella.
However, it now remains to be seen if the Swiss No11 will be fit to take on the European champions and World Cup favourites in Durban in eleven days time.
Behrami will be desperate to appear in South Africa, having been limited to just two minutes of action at Germany 2006.
Elsewhere, Jonathan Spector had a watching brief as the United States secured an impressive 3-1 friendly victory over Australia at the Roodeport Stadium in Johannesburg.
The Hammers right-back was left on the bench by US head coach Bob Bradley, who will now have to decide between Spector and Hannover 96 defender Steve Cherundolo when the Americans take on England in their opening Group C fixture in Rustenburg on Saturday 12 June.
In the England camp, Matthew Upson is expected to return to training on Sunday after missing Saturday's session due to a high temperature.
Upson and club-mate Robert Green will both hope to be involved from the start when the Three Lions contest their final warm-up fixture against the Platinum Stars team at the Moruleng Stadium in Rustenburg on Monday.
Manager Fabio Capello is expected to field his first-choice lineup against the local side ahead of Saturday's vital meeting with the US.
Meanwhile, Rio Ferdinand's knee injury has led to his fellow Academy graduate Frank Lampard being named as vice-captain for the tournament.