Photo: Photosport
Football's world governing body Fifa has been warned players are willing to go on strike if they continue to be overworked.
Professional Footballers' Association chief executive Maheta Molango believes players are now at breaking point.
The PFA has been calling for action to alter the congested football calendar, especially with the expanded 32-team Club World Cup proposed for next summer.
"I can tell you a situation not even 10 days ago where I went to a dressing room directly affected and I said: 'I'm happy to be here and bark a bit but ultimately it's down to you. How far would you like to go?" said Molango, speaking at the PFA and world players' union Fifpro's end-of-season review of player workload and recovery.
"Some of them said: 'I'm not having it, we may as well strike.' Some said: 'what's the point? Yes I'm a millionaire but I don't even have time to spend the money'.
"It's not even the union who has said it, it has been Jurgen Klopp and Pep Guardiola. We have reached a point where we cannot discount any action."
The PFA has threatened legal action and has been exploring options to do that over the growing number of games in the football calendar.
In conjunction with the PFA, a letter was sent to Fifa in May by Fifpro and the World Leagues Association (WLA) - which includes the Premier League - threatening legal action if it continues with plans to host a 32-team Club World Cup at the end of next season.
In a letter addressed to Fifa president Gianni Infantino and general secretary Mattias Grafstrom, seen by BBC Sport, Fifpro and the World Leagues Association say if Fifa extends its own competitions then it should alter others.
It adds that "imposing the burden of adaptation on national leagues and players is inherently abusive" and is "jeopardising national leagues and affecting the health and wellbeing of players".
However, BBC Sport understands Fifa believes it has taken into account player welfare with their scheduling programme
Molango added: "Some of the changes in England with the domestic calendar is forced by what Fifa and Uefa have done. What has happened, even further confirmation something has to be done but also that it's not affecting just the top players.
"We will always try to exhaust all diplomatic avenues, we have sent a letter, we have received an answer but unfortunately time is against us.
"Sometimes between grown up people, despite trying very hard to find solutions you need a third party to decide, maybe an arbitrator or a tribunal."
A study focused on young players warned how much stress their bodies are under and highlighted the number of minutes Real Madrid and England's Jude Bellingham has played before he is 21.
The midfielder, still just 20, has played 18,486 minutes in his career, compared to the 3,929 David Beckham played and 6,987 minutes Frank Lampard played at the same age.
Fifpro's Europe president David Terrier also warned players were burnt out, physically and mentally.
As part of the review of this season a survey of players showed over 50% of respondents said they had been played while carrying an injury.
"There is an emergency - we are in danger," said Terrier. "Players have gone beyond the limit and the international timetable is full to the brim."
Infantino addressed the issue of the football calendar with members associations at a Fifa congress earlier this month.
"Fifa is organising around 1% of the games of the top clubs in the world. 98-99% of the matches are organised by the different leagues, associations, confederations," he said.
"Fifa is financing football all over the world. The revenues that we generate are not just going to a few clubs in one country, the revenues that we generate are going to 211 countries all over the world.
"Our mission is to organise events and competitions, and to develop football around the world because 70% of the Member Associations of Fifa would have no football without the resources coming directly from Fifa."
- BBC