Joachim Low slammed "sloppy" Germany as the world champions crashed to a 2-1 defeat by Austria on Manuel Neuer's comeback to leave them winless in their last five games.
"If we play like that in Russia, then we have no chance," fumed Germany manager Low in Klagenfurt on Saturday.
Less than two weeks before the World Cup kicks off in Russia, Germany have now suffered back-to-back defeats after also sliding to a 1-0 loss to Brazil in Berlin in March.
The good news from a German perspective is that Bayern Munich goalkeeper Neuer looks set to go to the World Cup, having proved his fitness despite eight months on the sidelines due to injury.
However, when the Germany defence buckled in the second half, Neuer was powerless to stop Martin Hinteregger and Alessandro Schoepf scoring after Mesut Ozil had given the Germans an early lead.
"That was a good comeback from Manuel Neuer after so long out," Low said. "He made one or two outstanding saves, but the defeat annoys me.
"We didn't put into practice what we had planned.
"After the break, we fell into a pattern which I didn't like at all and we were far too sloppy in our game going forward."
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However, Low was keeping calm with one eye on the World Cup.
"There is a lot of work to do, but we won't drive ourselves crazy," he said.
"In two weeks, the team will be very differently prepared and I won't be having sleepless nights."
Low left out World Cup winners Thomas Muller, Toni Kroos, Mats Hummels and Jerome Boateng, but the Germans only controlled the rain-delayed game for the first half an hour.
Low declined to comment when a poll by national broadcaster ZDF showed the majority of German fans would rather see Barcelona goalkeeper Marc-Andre Ter Stegen than Neuer play at the World Cup.
Both Neuer and Ter Stegen are set to fly to Russia.
Despite missing 259 days with a fractured foot, Neuer looked sharp but Low says he will see how his goalkeeper's problematic left foot reacts on Sunday.
This was Austria's first win over their neighbours in nearly 32 years - dating back to October 1986 when Rudi Voeller scored West Germany's only goal in a 4-1 defeat in Vienna.
Austria's match-winner still sees Germany as among the favourites to defend their world title in Russia.
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"It's always fun to win, but it is especially nice against Germany," said Schalke midfielder Schoepf.
"But they have some quality players and are still one of the favourites for the title."
Low must cut four names on Monday before Germany name their final 23-man World Cup squad and several players have reason to worry.
"After the break, we couldn't find a structure that deserved to win against Austria," said Nils Petersen.
The Freiburg striker was the top scoring German in the Bundesliga, but is one of the chief candidates to be axed after making his debut for 76 minutes against Austria.
"I'll keep calm and let myself be surprised by whatever happens on Monday," said the former Bayern Munich striker.
Germany play Saudi Arabia in Leverkusen on Friday in their final warm-up match before facing Mexico in Moscow in their opening World Cup match on June 17.
