The former Gladbach midfielder says that his nation's outing against Portugal was a reality check that must remind them of the distance between themselves and the title
A Mario Gomez goal just under 20 minutes from time got Joachim Low's side off to a winning start in Euro 2012, but it could have been a different story on the night, with Paulo Bento's men striking the woodwork twice, and forcing Manuel Neuer into a number of impressive saves.
And Netzer, who won Euro 1972 as a player, believes that Germany's performance was far from what the public expected, and proved that there are a number of issues to be tackled by the Nationalelf if they are to lift the trophy on July 1.
"Germany's first game was assuredly far from what we would have imagined," Netzer wrote in a column for Bild.
"Although we were victorious in the end, the game was in no way satisfactory and hardly justified the high expectations we had in the team coming into the tournament.
"We lacked pretty much everything in the first half, there was no general direction, as if no player wanted the ball. The build-up play was way too slow.
"There were none of the things we saw from this team in the past which led to Germany being hailed as a favourite in this competition."
Germany's next game, against arch-rivals Netherlands, kicks off at 20:45CET on Wednesday, and Netzer told his compatriots that they can expect a very different showing from the Dutch, who slipped to a surprising 1-0 defeat against Denmark in their opening game of the tournament.
"We did not see the right Netherlands [against Denmark]. After this game, the Dutch will have a huge motive to stay in the competition," he warned.