Nigeria captain Nwankwo Kanu is doubtful for Sunday's African Cup of Nations quarter-final against hosts Ghana.Kanu injured a knee ligament minutes before Nigeria's opening match of the tournament against the Ivory Coast on January 21. Although he still played in that game, he has been sidelined since.Officials said Kanu, who did light training on Saturday, was unlikely to make the squad for the game.Kanu's unavailability would have added to coach Berti Vogts woes after Nigeria only scrapped through to the quarter-finals ahead of Mali on goal difference."Ghana are obviously the big favourites for this match, we have to admit that. But I believe can win this match, even if in extra time," Vogts said.Vogts said he had no explanation for the team's poor start to the competition. They failed to score until the second half of the last of their three Group B games."We played poorly in the first games and for that there can be no excuses. But I believe we have turned the situation around. You can see it in the body language of the players," Vogts added.Nigeria last won the continental title in 1994.Source: GHP