FORTALEZA, Brazil (AP) -- Germany midfielder Sami Khedira is mystified as to why some teams, including his own, seem to run into problems in their second matches at big tournaments.
Already at this World Cup, Italy has lost to Costa Rica 1-0 after defeating England 2-1 in its opener; the Netherlands had to come from behind to edge Australia 3-2 after demolishing defending champion Spain 5-1 in its opener; and Brazil was held 0-0 by Mexico.
''I can't explain why the second match is always hard after a win. I think it's a mental thing,'' Khedira said Friday. ''We went through the same experience in 2008 and 2010. We don't want to come to the last game and worry.''
Germany has twice lost its second match in recent tournaments - 2-1 to Croatia at the 2008 European Championship and 1-0 to Serbia at the 2010 World Cup, despite beating Australia 4-0 in the opener.
In Brazil, the Germans opened in Group G by defeating Portugal 4-0 and next play Ghana on Saturday. After the loss to Serbia four years ago, Germany edged Ghana 1-0 to advance to the knockout stage.
''We will be totally focused against Ghana. It's an African team and they are very athletic. So we have to concentrate. And I think we will prevail. We have to be tactically clever,'' the Real Madrid defensive midfielder said.
''We beat them four years ago, but it was a difficult match and we needed some luck,'' Khedira added. Germany won with a second-half goal by Mesut Ozil.
Today, both Khedira and Ozil are still seeking to reach top form. Khedira was out for six months with a knee injury and only returned shortly before the World Cup, while Ozil's form dipped, amid injury problems, after a promising start with Arsenal.
Despite confidence in Germany's strengths, Khedira expects a tough match.
''Ghana has excellent players who play in good clubs. They don't give up, they are robust and they are technically good,'' he said.
Germany coach Joachim Loew said the second match presented as great a challenge as the opening match and that it was ''a psychological problem'' for teams to keep concentrating after achieving a good start.
''You can't have any lapses. If there's a lapse, you will lose,'' Loew warned on Friday. ''Their situation is that it's a final for them.''
Ghana lost 2-1 to the United States in its opener and Germany knows it will be a long, hard game on Saturday.
''They will fight until they bleed,'' Loew said. ''They can attack very well, they are quick, ready to march on for 90 minutes. We have to defend well and be ready to attack with lightning speed once we win the ball.''