The roots of Germany's destruction of Brazil can be traced back to a resounding U-21 victory over England five years ago, according to Per Mertesacker. Germany produced one of the biggest shocks in FIFA World Cup™ history on Tuesday night when they beat the hosts 7-1 in Belo Horizonte.

A quick glance at the team sheet shows the performance has been a long time in the making. Shortly after their group stage exit at UEFA EURO 2000, the German Football Association initiated a root and branch reform of its youth development.

The Germans had to be patient, but their reforms paid off in 2009 when the U-21 side won the UEFA European Championships in Sweden, sweeping England aside 4-0 in the final. Six of the XI that played that night in Malmo also participated in the win over Brazil on Tuesday evening.

"It started off in 2009 when we won the Under-21 tournament and beat England 4-0. I think there's a small link between these two tournaments," Germany defender Mertesacker said. "The 2009 tournament was a real turning point. The youth academies started developing well over the last five or six years."

The sextet of stars who played in Malmo that night - Manuel Neuer, Benedikt Howedes, Jerome Boateng, Mats Hummels, Sami Khedira and Mesut Ozil - now have 270 senior caps between them. They are supremely talented individuals, but they are also team players. Team unity, harnessed by coach Joachim Low, has been key to Germany's success during Brazil 2014.

"We have one of the strongest squads I've ever played in," said Mertesacker, who won his first cap ten years ago under Low's predecessor Jurgen Klinsmann. "We have two excellent players for every position and everyone believes in each other. We have created excellent team spirit during the tournament and with those magnificent players growing up together it makes it easier."

We have one of the strongest squads I've ever played in

Germany defender Per Mertesacker

Mertesacker hopes Tuesday's semi-final win will not be the peak for this Germany team. He wants to lift the biggest trophy in world football on Sunday at Estadio Maracana. But for now he is more than happy to reflect on the most impressive Germany win for many a year.

"It's the best result of my career when you consider the importance of the game. I could not believe it," said the Arsenal defender, who came off the bench at half-time. "It was crazy to watch us score five goals so early. Everything went so fluently. We played through their lines, found always a player who was completely free in front of the goal. We showed some great skills, some great passing moves. It was nice to watch."

So comprehensive was the win that Mertesacker was almost apologetic towards the dejected Brazilians.

"I feel sorry for them," the 29-year-old said. "I experienced that when I played with Germany in 2006 we got knocked out by Italy in the semi-final. The expectations are big here in Brazil and to carry those is not easy. You could see that and we took advantage of it because there was a bit too much pressure on them and I feel sorry for everyone."