Bayern Munich captain Philipp Lahm said his side were "careless" in their surprise defeat to Rostov and must cut out the mistakes.
The Russian side had never won a Champions League group game before Wedneday night but knocked off one of the continent's most decorated sides 3-2 in sub-zero conditions at the Olimp-2 stadium.
Both sides had taken the lead and lost it again - Douglas Costa and Juan Bernat on target for Bayern with Serdar Azmoun and Dmitry Poloz replying for the hosts - before the game was settled by Christian Noboa's fine free-kick.
While Bayern had already assured themselves a place in the knockout stage, the shock reverse ensured they surrendered top spot in Group D to Atletico Madrid and made it three games without a win after taking one point from their last two Bundesliga outings.
Assessing the match, as well as Bayern's dip in form, Lahm said: "We wanted to win here, but we didn't succeed. We're a little too careless at the moment. We have to be aware our opponents might score, and that mistakes will be punished.
"We're making too many of them at the moment. I don't know why that is, but we must get rid of it as fast as we can.
"As Bayern, we have to be winning this game. We had enough quality on the pitch, there were enough internationals out there - rotation is no excuse for the defeat."
Manager Carlo Ancelotti was in similarly downbeat mood, conceding his team are off their game at present.
"We're finding things very difficult at the moment," he said.
"We made too many mistakes. We didn't play well, and that's why we lost. We did not underestimate Rostov."
There are also concerns over defender Jerome Boateng, who was withdrawn with a thigh injury in the second half and could miss the weekend.
"Jerome Boateng is rated doubtful for FC Bayern's Bundesliga meeting with Bayer Leverkusen on Saturday," read a brief statement on the club's website.
"Boateng will undergo a thorough examination on arrival in Munich on Thursday for an exact diagnosis."
For Rostov coach Ivan Daniliants it was an an achievement to savour.
"This game with Bayern was a great event and this is a glorious victory of our guys," he said.
"They have felt the full extent of the love of all our fans, even those who are far from the city and the country. I have received many messages and from Kazan and other cities.
"This victory is a special line in the history of our football."
Source: PA-WIRE
