Joachim Low fears Wayne Rooney could "explode" into form when Germany meet England in the last 16 of the World Cup in South Africa on Sunday.
He said: "Rooney may not have been a big gun so far but he is always ready to explode, he is difficult to mark and control so our defence will need to watch that he doesn't score."
It will be the first meeting between the two nations in the World Cup finals since West Germany beat England on penalties in the 1990 semi-finals, and Low is already relishing the match.
"We are looking forward to taking on England, it's always special for us. There is a great history in the World Cup between England and Germany," he said.
"I've watched England's matches so far, they were struggling in the first two matches but that is quite normal, sometimes you only pick up speed as you go through the tournament. They haven't shown the best of form so far but make no mistake, this is a wonderful team. England have enormous experience so this team is going to be incredibly dangerous."
Low will be hoping for speedy recoveries from Jerome Boateng (back) and Bastian Schweinsteiger, who has a muscle injury. Ozil also suffered a minor knock against the Ghanaians, who look set to be Africa's sole representatives in the last 16 after they took second place in the group on goal difference from Australia.
Ghana's Serbian coach Milovan Rajevac said: "I am delighted that my side Ghana is the only African side to reach the knockout phase. I'm still trying to come to terms with the situation. We have now got the next match against the United States (on Saturday), so we don't have much time to be enthusiastic about this win as we have to think about the next game.
"I think the majority of South Africans will now support Ghana, we're the only African team left so I hope we will benefit from massive support."
Ivory Coast could still join Ghana in the last 16 but it would require a huge goal difference swing in their favour for them to overtake Portugal and claim second place in Group G while South Africa, Nigeria, Algeria and Cameroon are already out.
