Ghana's Kevin-Prince Boateng has urged his teammates to "fight to the death" against Germany.
The Germany-born midfielder was on the bench for his side's late 2-1 defeat to the U.S. and came on in the second half as they battled to come back from 1-0 down.
He said it would be tough to get their campaign back on track against Joachim Low's in-form side, who demolished Portugal 4-0 in their opening game.
"I was surprised that I did not start [against the U.S.] -- but apparently the coach had other ideas," he told reporters at a post-match interview.
"We know we have to take all three points now, and we also know that won't be an easy task against Germany. But we will prepare for it and try to give it our all once again."
Boateng, the half-brother of Germany defender Jerome, played for the German under-21 team until 2009, but later opted to represent Ghana, the country where his father was born.
The two are set for their second World Cup meeting on Saturday, and Kevin-Prince Boateng said: "It's about time I finally beat my brother, even though Germany were in great shape against Portugal.
"I will do all I can to be successful with Ghana. Nobody can predict if that's enough for the World Cup trophy, but we are allowed to dream and to have such goals.
"It's just like in the old Rome. There are people watching on the sidelines want to see two teams battle it out. Whoever wants it more wins it, and that's why we will fight to the death against Germany."