Niko Kovac pointed to a lack of determination from his players as he assessed Bayern Munich's 2-1 defeat to Hoffenheim, admitting the Bundesliga champion made "too many mistakes".
Bayern was unbeaten in 20 Bundesliga matches going into the clash with Alfred Schreuder's side but failed to carry the momentum from its midweek thrashing of Tottenham in the Champions League into its domestic campaign.
Hoffenheim's Armenian striker, Sargis Adamyan, making his first league start of the season, was afforded opportunities from the outset and he capitalised in the 54th minute, scoring his first goal for the club.
Robert Lewandowski levelled for Bayern 19 minutes later but the parity was brief as Adamyan struck again and ended his team's four-game winless streak.
Kovac vented his disappointment after the game, saying: "Unfortunately we couldn't take the good feeling from Tuesday into today - that frustrates me.
"The first half was okay, we created some good situations, but should have played with more determination.
"We didn't do well in the second half, we made too many mistakes and never put our opponents under pressure. In the end, Hoffenheim's win wasn't undeserved."
Opposite number Schreuder hailed Adamyan's full debut as "a dream" and praised the courage of his players after it picked up only its second league win of the season.
"I am very proud of my team," said Schreuder. "It's the first time that Hoffenheim have won here.
"The lads showed a lot of passion and courage and I'm happy to be the head coach at this club.
"Sargis needed some time and he earned his place in the starting 11. He senses trust from his team-mates and for it to go as it did for him is, of course, a dream."