Loyalty is a difficult concept in football.

Fans who sacrifice time and money to follow their team expect their unconditional support to be repaid by the players on the pitch.

Clubs too have a right to demand a degree of loyalty from players in whose development they may have invested considerable resources – both financial and personal.

But, one-club-legends such as Paul Scholes, Francesco Totti, Steven Gerrard and Philipp Lahm aside, players measure loyalty in different ways. For many, loyalty has a limit which can be reached as soon as the next club offers better sporting prospects or a chunkier pay packet.

To an extent, this is understandable. Loyalty to a club may be non-negotiable for supporters but, for the players, football is a professional career. It's a team game but, ultimately, personal development often trumps all other considerations.

Enough is enough

But none of that excuses Pierre-Emerick Aubameyang's behavior over the last 15 months.

In October 2016, the Borussia Dortmund striker was suspended by Thomas Tuchel for a Champions League group game away at Sporting Lisbon, the former BVB coach citing "internal issues."

In November 2017, Tuchel's successor Peter Bosz also saw it necessary to suspend the Gabonese forward after he invited a camera team from the Austrian energy drink brand Red Bull into Dortmund's training center to film a promotional video.

This weekend, ahead of Dortmund's Bundesliga game against Wolfsburg, a third successive coach, Peter Stöger, decided to omit Aubameyang from the squad after the player left training early and failed to attend an important team meeting.

"You reach a point where you can't tolerate it anymore," said sporting director Michael Zorc after Sunday's goalless draw. "I don't know what's going on inside his head. We're not used to this behavior from him. It can't go on like this."

"I support the decision," added goalkeeper Roman Bürki. "There are rules which apply to every player regardless of how many goals he scores or prevents. It was a logical decision. It would be a shame if he missed out again due to his stupid actions."

Bürki is absolutely right – and Zorc really shouldn't be surprised. After all, Aubameyang has made no secret of his intention to leave Borussia Dortmund one day and of his dream to play for Real Madrid.

That is his prerogative but, over the last 15 months, Aubameyang has repeatedly put his own interests ahead of the club who pay his wages, the teammates who set up his goals and the supporters who cheer his name.

Fans losing patience

Not that they'll be cheering his name any longer. Insiders among the club's hardcore support have long stopped caring about whether Aubameyang stays or goes. As they demonstrated when they chanted Jakub Blaszczykowski's name despite his transfer to Wolfsburg, loyalty is important to them, just as important as performances. 

Individual indiscretions can be - and, in the case of Aubameyang, have been - excused so long as a player's performance levels remain high and the atmosphere within the dressing room remains unaffected.

That line has now been crossed and Dortmund should make sure he leaves quickly, because no individual is more important than the collective.