Bayern Munich coach Jupp Heynckes has said he would not sign players such as Ousmane Dembele and Pierre-Emerick Aubameyang after Borussia Dortmund's problems with them.
Dembele moved to Barcelona in the summer after effectively going on strike and missing training, for which he was suspended, while Aubameyang, who missed two team meetings last week, has been linked with Arsenal.
"The Dembele and Aubameyang situations have to be viewed in a critical light," Heynckes told a news conference.
"It's unacceptable how certain players act in professional football. It's just not right. These situations have always happened, but now they have reached a whole new dimension.
"I am very critical of this because players are very privileged. The [Philippe] Coutinho transfer was similar but solved more elegantly.
"Ethics and morals form part of our job and we have to look at the bigger picture and what's happening in society. You have to consider how difficult it is for others to earn their monthly income.
"Clubs signing these players have to expect that this behaviour will continue at their club.
"I don't want to speak of solidarity, but it's a team sport where you cannot afford to set your own individual targets. Clubs should think twice about signing these players. Honestly, I would reject it."
Heynckes said he "couldn't imagine" such a situation happening at Bayern and added: "You have to show the player that it is not possible.
"It is, of course, a question of mentality. Players have a responsibility and it's not a case of money going into their bank accounts at the end of the month.
"Banishing the player to the stands is not the way. You have to work at it, communicate and care for the player. You need a clear direction and I think we have that at Bayern Munich."
Heynckes repeated his plea to clubs "to be careful not to alienate the fans," having voiced support for supporter protests against high ticket prices for Bayern's Champions League game at Anderlecht in November.
He said: "Our fans correctly criticised Anderlecht for hiking ticket prices up to €100, while Arsenal haven't had any success in recent years yet continue to increase tickets prices.
"It's just a hobby for our fans, and they sometimes have to take a day off work."
Meanwhile Heynckes confirmed left-back David Alaba will miss the weekend game against Werder Bremen with a stomach bug.
Mats Hummels returned to training on Friday after a heavy cold but will not be risked against Bremen, while Robert Lewandowski returns to the squad after injury.