Ghana have dispelled doubts over their chances of winning a fifth Africa Cup of Nations title following their lacklustre display against Guinea.
The Black Stars topped Group D on Wednesday, but only after drawing 1-1 with the Guineans, who were reduced to 10 men in the second half.
Assistant coach Kwesi Appiah says his side will improve for Sunday's quarter-final against Tunisia in Franceville.
"I believe we will raise our game to reach the semi-finals," he said.
"In our opening game against Botswana, we did not play at our level. But for the second game against Mali, we played at about 70 per cent of our capacity.
"Every game is different and we will treat them so."
John Pantsil, who captained the four-time champions against Mali and Guinea in the absence of John Mensah, said he expects Tunisia to prove tough opposition in the last eight.
"This is a crucial and tricky game," the full-back said. "It won't be easy because Tunisia are a very good team, who pass the ball around very well."
Ghana are buoyed by the news that Mensah will be fully fit for this quarter-final, after a thigh injury forced the Black Stars captain to watch the Guinea game from the bench.
The defender scored the winner in the 1-0 defeat of Botswana prior to his red card, so prompting his suspension from the win over Mali, but his return will help against forwards like Issam Jemaa and Youssef Msakni.
"It will be difficult against one of the best teams in this competition," added star striker Asamoah Gyan.
"But we will rise to the occasion because with the Ghanaian character, we will always handle the pressure."
Ghana, who won the trophy in 1963, 1965, 1978 and 1982, have been studying the Carthages Eagles as the West Africans seek to end their 30-year wait for another Nations Cup title.
"We have watched video tapes of Tunisia, and they are a very good team," Appiah added.
The teams last clashed in a 2006 friendly, which the North Africans won 1-0.