Hoffenheim owner Dietmar Hopp has confirmed the sale of Luiz Gustavo was one of the main reasons for Ralf Rangnick's departure from the club.
Rangnick and Hoffenheim parted company after four and a half years together by mutual consent after the Brazilian midfielder was sold to Bayern Munich behind the coach's back.
Negotiations between Hopp, Hoffenheim's general manager Ernst Tanner and Bayern representatives over the transfer of Gustavo were conducted without Rangnick's knowledge or consent before Christmas.
When Rangnick got wind of the negotiations, he acted with amazement and claimed the transfer would "send the wrong signal'' and that he firmly opposed the deal. Nevertheless, the transfer went through on Saturday evening and Rangnick was no longer Hoffenheim's coach less than 24 hours later.
"Rangnick felt as if he had been made out to be a liar (for denying negotiations had taken place),'' Hopp told Bild. "He asked himself whether it made any sense continuing as coach.''
Rangnick reiterated his disappointment at not being consulted on the Gustavo deal.
"I just gave my personal, honest opinion,'' said Rangnick. "I made it clear that I could not understand why I had not been informed of the negotiations earlier.
"I asked for a vote of confidence and suggested that we should both consider the future during the festive period.''
According to Bild, shortly before concluding the deal with Bayern, Hopp told Rangnick in an email that "it would be better to go separate ways''.
Rangnick's assistant Marco Pezzaiuoli will take charge of team affairs.