Leon Goretzka said Bayern Munich only had themselves to blame after letting a two-goal lead slip in a dramatic 3-2 defeat to Borussia Monchengladbach on Friday.
Robert Lewandowski and Goretzka were on target to put the European champions in command after only 26 minutes at Borussia-Park, but the hosts came storming back.
Jonas Hofmann struck twice and Florian Neuhaus gave Gladbach the lead four minutes into the second half as the leaders fell to pieces.
The Bavarian giants were unable to prevent seeing their 20-match unbeaten run come to a stunning halt, and the 24 goals they have conceded from 15 games is their worst defensive record at this stage of the season since the 1981-82 campaign.
Midfielder Goretzka knows Bayern must tighten up in their quest for yet more honours.
"Giving the game away like that after leading 2-0 hurts. The first 30 or 35 minutes were the best we've played in a long time," he said.
"We were in control, but then we lost the ball twice where we shouldn't lose it and didn't react properly. Then it's 2-2 in no time. Their winner comes from a similar situation. We invited the opponent three times and they took their chances.
"Then you're behind and it doesn't get easier when a team is able to just concentrate on defending. In the second half, we had a bit of bad luck here and there.
"They were individual mistakes, but you can still position yourself better beforehand so that these ball losses are not so devastating. We are conceding too many goals against at the moment."
Hofmann now has six goals from 14 goals in all competitions and the winger felt Marco Rose's side exploited Bayern's high defensive line superbly.
He said: "We're over the moon. It was a tough fight. After going 2-0 down, I'm sure many didn't expect us to be able to turn it around. We scored the first two goals exactly as we had imagined.
"Bayern defended with a very high line, so we had to get behind the back four. We did that very well. We had a hard time at the start, but we got into the game more and more.
"It was great that we took the lead right after the break. In the end, it was a tough battle defending that all. That's part of it, especially against Bayern."
Gladbach's victory put them level with Werder Bremen on 26 Bundesliga successes against Bayern, a total that no side has bettered.