According to a Football Federation Australia (FFA) statement, Wilkshire arrived in camp carrying the injury.
After being assessed by medical staff, Wilkshire was deemed not fit enough to train or play in Brasilia on Saturday and was released back to Russian Premier League club side Dinamo Moscow.
It has become common practice for injured players to have to make lengthy journeys to link up with their national team and have their fitness assessed, after a succession of high-profile incidents in which players were withdrawn from international duty only to play club football shortly afterwards.
FFA confirmed no replacements will be called up for Wilkshire or Cahill, who injured his ankle playing for New York Red Bulls last weekend.
Wilkshire's absence means Ryan McGowan is likely to start at right-back in the friendly international at Estadio Nacional Mane Garrincha, which kicks off at 5.15am on Sunday (AEST).
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