Borussia Dortmund coach Thomas Tuchel believes some fans "went too far" in their rough treatment of Mats Hummels in Saturday's 5-1 win over Wolfsburg.
Hummels captained Dortmund at Signal Iduna Park, despite requesting a transfer to bitter rivals Bayern Munich in midweek.
The Germany defender hit out at "nonsense" suggestions that he had approached Bayern over a move, but regardless his name was booed before Saturday's 5-1 win over Wolfsburg, before his every touch was whistled and the 'Yellow Wall' raised a banner which read: "The captain is leaving the ship. The sooner, the better!"
While Tuchel admitted the backlash was to be expected, he expressed sorrow that some had spoiled the game's atmosphere.
"It wasn't hard to imagine that the fans would want to give voice to their dissatisfaction," Tuchel said.
"A very ambivalent mood could be felt in the stadium.
"He was whistled whenever he was on the ball at first, but then the majority of the crowd attempted to drown that out with applause and take a stand.
"It is not pleasant for your captain to have to deal with such an atmosphere in your own stadium. I think there is a difference between whistling and offensive songs which go too far in their content."
Tuchel insists that despite the supporters' fury, Hummels remains well supported among his Dortmund team-mates.
He added: "Since this came to light on Thursday, there has been a strong feeling of solidarity.
"The team is a tight-knit group. Mats was able to rely on his team mates continuing to play with him as normal - irrespective of what happens.
"That gave him the sense of security to allow him to stay calm and relaxed, and to play a strong game."