Joachim Low's men progressed to the World Cup final in emphatic fashion, routing host nation Brazil 7-1 in Belo Horizonte on Tuesday.
Of the seven goals scored at the Estadio Governador Magalhaes Pinto, five came before the half-hour mark as Germany produced a devastating period of football in their quest for a fourth World Cup title.
With Germany and Argentina, who have kept a tournament-high four clean sheets, set to go head-to-head at the Maracana in Rio de Janeiro on Sunday, Mertesacker said his team must maintain the same level of performance if they are to claim their first World Cup since 1990.
Coincidently, Germany - known as West Germany at the time - overcame Argentina 1-0 to win the 1990 showpiece at the Stadio Olimpico in Rome.
"We must play the same way that we did against Brazil, otherwise we have no chance," said Mertesacker, who was a second-half substitute against Brazil.
"Our performance against Brazil was nearly 100 per cent. If you look at the stats, the passing, the goals we scored, everything was so fluent. But if we drop five per cent then we will have no chance.
"(Winning 7-1) is dangerous for us. We can't lose our focus now because we scored seven goals. We must keep calm and be aware of the situation. Our main target is to win the final.
"We want to finish on a high. We want more history. We don't want to just settle for this result before the final."
