Toni Kroos' mistake proved costly as Real Madrid's goalscoring problems continued on Tuesday with a surprise 1-0 defeat to CSKA Moscow in the Champions League.
Gareth Bale and Sergio Ramos were among a number of key players missing at the Luzhniki Stadium but it was Kroos' dreadful backpass that allowed Nikola Vlasic, on loan from Premier League Everton, to put CSKA ahead after just 68 seconds.
Madrid searched for an equaliser but, despite hitting the woodwork three times, was resisted by a determined CSKA defence. The reigning European champions have now failed to score in three consecutive matches.
CSKA's veteran goalkeeper Igor Akinfeev was sent off deep into added time after picking up two yellow cards for dissent but nothing could spoil the hosts' victory which lifted them above Madrid in Group G.
Julen Lopetegui's side lacked spark, thrust and cutting edge in attack. They missed Bale, Isco and, perhaps even, the lethal touch of Cristiano Ronaldo.
"Goals come when you keep creating chances and believe you will be more accurate," Lopetegui said.
"That is all we can do. I am sure we will soon be scoring again and winning again."
Some of the changes were enforced, with Isco and Marcelo out injured, but Bale and Ramos were left at home to rest and Luka Modric started on the bench.
Madrid were three down by half-time against Sevilla last week and this time they were behind within two minutes.
It was self-inflicted as Kroos tried to half-volley a bouncing ball back to Navas but Vlasic read it and intercepted. Raphael Varane was slow to react and the weaving forward finished into the corner.
CSKA coach Viktor Goncharenko said biggest concern was that his players would slump after the high of a remarkable victory.
"We played agressively, boldly, we defended really well. Of course an early goal helped us a lot," he said.
"Now we will all enjoy the evening. I'm afraid my players' emotions will come down after this win. Hopefully because they are young they will survive it without any serious damage."