Bayern Munich captain Philipp Lahm told SportBild on Wednesday of the "incomprehension" among his teammates at the negative reaction from fans to the signing of Manuel Neuer.
"Nobody within the squad can understand the reasons behind the hostile protests against Manuel Neuer," said the German international full-back.
Booing opponents may be part and parcel of the game but as Lahm pointed out, "the fans should offer their unconditional support to their own players".
"By protesting against Manuel Neuer they are really protesting against the team as a whole."
Lahm also hit out at the five supporters' groups who issued Neuer with a code of conduct following his arrival from rivals Schalke 04 earlier this summer.
SportBild revealed that the code of conduct banned Neuer from starting chants with the supporters, and also prevented him from approaching the fencing at the front of the Allianz Arena's south stand, where the hostile fan groups stand during matches.
In addition, the code prohibits Neuer from kissing the Bayern badge on his shirt.
SportBild also reported that a meeting will take place on July 26 in Munich between Neuer's agent, his public relations advisor and the Bayern board in which they will decide how to respond to such a hostile attitude on behalf of these fans.
Neuer was born in Gelsenkirchen and was on the books at his hometown team Schalke for 20 years before joining the German champions last month.
He was given a warm welcome by the majority of the club's fans, but he did little to win over his doubters in Tuesday evening's 2-1 friendly defeat to Hamburg.
Neuer was at fault for Hamburg's first goal in the match played in Mainz, coming out of his goal but failing to deal with a free-kick, which was then turned into the net by Son Heung-Min.
The match was part of a four-team pre-season tournament also involving Borussia Dortmund and Mainz.
Dortmund beat the hosts in the evening's other game, meaning they will now face Hamburg in Wednesday's final, with Jupp Heynckes' Bayern facing Mainz in a play-off for third place.