Bayern Munich coach Hansi Flick admitted it was errors by the European champions which cost them a 3-2 Bundesliga defeat at Borussia Moenchengladbach.
The league leaders suffered only their second loss this season, which could cost them top spot if second-placed RB Leipzig beat Borussia Dortmund at home on Saturday.
"Gladbach were very efficient, they brutally exploited three mistakes by us," Flick said.
"We played good football for the first 30 minutes and dominated the game, but it was little things that decided the match - mistakes by us, ball losses, some poor defending.
"The individual mistakes hurt us because they were punished and after going 3-2 down, we couldn't come back as we had hoped. We have to blame ourselves for this defeat."
Bayern were cruising at 2-0 up after 26 minutes thanks to a Robert Lewandowski penalty and a superb Leon Goretzka goal at Borussia Park.
However, Gladbach roared back as midfielder Jonas Hofmann scored twice to make it 2-2 at the break, then set up Florian Neuhaus who scored what proved to be the winner for the hosts just after the break.
"We scored the goals exactly the way we set out to score them," said Hofmann.
"We got better and better as the game went on, but in the end it was a hard fight."
Thomas Muller agreed with Flick that Bayern can only blame themselves.
"Our passing mistakes were punished - ice-cold. We lost the ball too easily going forward," Muller added.
"We made too little out of it when we laid siege to their goal in the second half."
In the pre-match build-up, Gladbach coach Marco Rose had highlighted Bayern's tendency to defend high up the pitch, which created space for opponents to attack, and his team ruthlessly exploited the weakness.
"We have to keep going - that's the key message I have just told the boys, we've had many games in which we didn't have much luck," said Rose, whose side still trail Bayern by nine points in seventh place.
"We worked for it, but overall it was deserved. I'm really happy for the boys, they did great."
