The Blackburn Rovers man is reported to be suffering from a problem in the meniscus of his left knee, with the injury likely to rule him out of Turkey's semi-final against Brazil in Saitama and possibly the final, should the Turks reach that match in Yokohama next Sunday.
Unsal was in pain following Turkey's well-deserved Golden Goal extra-time victory over Senegal in the quarter finals and his meniscus problem may need surgery, as it has bothered the former Galatasaray player in the past.
'Little Hakan' will remain with his colleagues in the Far East to support them, should he not be fit to play but his omission will be a blow to Gunes, who may look to Fenerbahce's Abdullah Ercan as his replacement for the Brazil re-match.
Unsal has had an eventful finals campaign, having been sent off in the team's first match against the Samba Boys for kicking the match ball at Rivaldo in the dying minutes of a controversial 2-1 defeat.
He will rue the chance to put things right against the South Americans on Wednesday and his injury may prove to be a headache for both Gunes and Rovers boss Graeme Souness, if indeed he needs to go under the knife.
