Thomas Muller described Germany's shock World Cup defeat to Japan as "ridiculous", but acknowledged Die Mannschaft's woeful defending meant they did not deserve a victory.

Germany looked set to make a positive start to their Group E campaign when Ilkay Gundogan put them ahead from the spot on Wednesday, but a remarkable comeback from Japan stunned the four-time winners.

Bundesliga pair Ritsu Doan and Takuma Asano came off the bench to score in a famous win for the Samurai Blue, leaving Germany under huge pressure ahead of Sunday's meeting with Spain.

Having lost their opening game just once in their first 18 World Cup participations (W13 D4), Germany have now started with a defeat at consecutive tournaments. 

Speaking to ARD after the reverse, Muller said: "In terms of feeling, we actually played a good game over long stretches. 

"Of course, a good game in football is also characterised by the fact that you convert the chances and superiority into goals. 

"The effectiveness at both ends didn't match. It's ridiculous that we are left with a defeat. 

"But at the end of the day, when you see what we're leaving behind us and how we conceded the goals at the end, you would say in football jargon that it's not an undeserved loss."

Germany captain Manuel Neuer, meanwhile, lamented the team's slow start to the second half in his own post-match interview.

"I'm totally frustrated and upset that we gave up the game," Neuer said. "That was more than unnecessary. We created a lot of chances to score, so luck and bad luck go hand in hand. 

"The imperative that we wanted to score the second goal was perhaps missing and we brought Japan back into the game. 

"After the break, we didn't have that flow of play any more, didn't play with the self-confidence we had in the first half. 

"It was a bit more difficult because they started higher, but we still have to play well."

Germany's defeat was their first after scoring the opening goal in a World Cup match since a shock quarter-final loss to Bulgaria at the 1994 tournament, ending their run of 25 such games without losing.

Hansi Flick's side must now bid to bounce back against Luis Enrique's men next time out, as they look to avoid consecutive group-stage World Cup exits.