Ghana's players are still down two days after their 2-0 World Cup Group E defeat by Italy in Hanover.
Kuffour's error led to Italy's second goal
"It's been two days now and I can't go to bed. It's been very bad for me," midfielder Sulley Ali Muntari told a news conference on Wednesday.
The Black Stars failed to threaten an organised Italian defence and fell behind to a goal from Andrea Pirlo.
A botched back pass from defender Samuel Osei Kuffour gifted Vincenzo Iaquinta the second goal.
"Kuffour is suffering more than anyone at this moment," said
coach Ratomir Dujkovic.
"He is very sorry for what happened. We will try to do everything to cheer him up."
Captain Stephen Appiah said Ghana could still reach the later stages.
"Teams that lose the first match can still get to the quarter-finals and go far," Appiah said.
One of Ghana's problems was a failure to convert ample possession in midfield into goalscoring chances.
Dujkovic said he was aware his side had problems up front but was not unduly troubled.
"We scored eight goals in friendlies," he said. "It does not mean we have a problem in attack.
"Even Brazil had problems in attack when they removed Ronaldo (in the second half)," he said referring to Brazil's 1-0 victory over Croatia on Tuesday.
"I think they (Ghana) will play much better and score goals against Czech Republic (on Saturday).
"I am still confident we can pass the group stage and get to the semi-finals."