Doctor Xavier Mir, who led the operation, expects the 29-year-old to be back in action in early April.

Deco sustained the injury on Saturday after colliding with a Recreativo Huelva player during the Spanish champions' 4-0 away win, causing him to be substituted midway through the second half.

"I just spoke with [Portugal coach Luiz Felipe] Scolari and told him it would be a pleasure to be with my team-mates for these two games, but I can't," said the former Porto midfielder.

"[Before the operation] I also talked with FC Barcelona doctors and we decided I couldn't wait any longer. So we opted to undergo the operation."

Scolari is also without the suspended Simao Sabrosa for the Belgium match on Saturday.

Portugal are four points behind Group A leaders Finland, with a game in hand.

Portugal squad: Daniel Fernandes (PAOK FC), Ricardo (Sporting Lisbon), Fernando Meira (Vfb Stuttgart), Jorge Andrade (Deportivo), Miguel (Valencia), Manuel da Costa (PSV Eindhoven), Caneira (Sporting Lisbon), Paulo Ferreira (Chelsea), Ricardo Carvalho (Chelsea), Petit (Benfica), Hugo Viana (Valencia), Joao Moutinho (Sporting), Raul Meireles (Porto), Tiago (Lyon), Cristiano Ronaldo, (Manchester United), Helder Postiga (Porto), Hugo Almeida (Werder Bremen), Nani (Sporting), Nuno Gomes (Benfica), Ricardo Quaresma (Porto), Simao Sabrosa (Benfica).