Carlo Ancelotti felt Bayern Munich were caught cold by in-form Hoffenheim after the runaway leaders suffered just their second Bundesliga defeat of the season on Tuesday.
Andrej Kramaric scored the only goal of the game midway through the first half, although the hosts deserved to be further ahead at the break after dominating Bayern in the opening 45 minutes.
Bayern improved in the second period but still could not find an equaliser as the champions lost to Hoffenheim for the first time in the 18th meeting of the two teams.
"Congratulations to Hoffenheim. We were a bit surprised by their play and weren't well organised in defence," Ancelotti told the club's website.
"It was a very intense match. Our first half wasn't so good. We did a much better job in the second half, we were more aggressive then. We had our chances to level the scores.
"But things just don't work out on certain days, that's football."
Arjen Robben echoed his coach's words, admitting Bayern paid the price for a slow start that saw them concede in league action for the first time in six games.
Robert Lewandowski came the closest to scoring for the away team. The Polish forward hit the bar as he attempted to turn home Kingsley Coman's low cross in first-half stoppage time.
"It's a pity, we mustn't allow that to happen. The first half was unnecessary. We lacked discipline, we were always a step too late, which is why we had problems," Robben said.
"The second half was much better, just as it should be. We were dominant and had our chances, but a goal refused to come today."