SL Benfica and Portugal midfield player Petit will be out for a month after suffering a broken jaw.
Petit, 26, suffered the injury during Saturday's 1-1 home draw with Clube Académica de Coimbra, when he was caught in the face accidentally by the Coimbra player Binho. The result left Benfica fifth in the Portuguese Super Liga.
'Don't rush back'
A Benfica official said: "He has had two plates fixed into the affected area and these will be taken out after three weeks. If all goes well, he will be able to play again eight days after that. The worst thing would be to rush him back."
Petit is expected to miss Benfica's next three league games and is also a doubt for Portugal's friendly against Scotland in Braga on 22 November.