The global players union FIFPRO is concerned that footballers are being asked to play too many matches in a short space of time as the sport restarts following the coronavirus stoppage and says there has already been an increase in injuries.
FIFPRO said in a statement on Friday that competition organisers "have so far failed to introduce safeguards to protect player health during what will be a highly-congested schedule."
"Now, since the restart we are seeing a first spike in injuries because of insufficient preparation time and congested match schedules," it said.
The current season was stopped for around three months in most European countries due to COVID-19 and domestic leagues are now rushing to finish by the end of July.
The Champions League and Europa League will conclude in August while the 2020/21 season will then get under way around mid-September, with national team matches squeezed in between.
Next season's Champions League group stage will be played in three months instead of four while a total of six rounds of international matches will be played in Europe in October and November, instead of the usual four.
FIFPRO said the response to the more intense fixture list should be "better and innovative safeguards" for player health rather than an erosion of existing rights.
"It is vital that stakeholders protect players and allow them to perform at their best," it said, adding that the issue could not wait until 2024 when a new international calendar is due to be introduced.
FIFPRO said that there should be a five to six week break between seasons, including around three week's holiday for the players. "It is not acceptable that altering competition calendars leads to pressure to breach these rights," it said.
It also warned against applying pressure or imposing disciplinary measures on players who put the health of themselves and families ahead of playing obligations.
(Writing by Brian Homewood; Editing by Toby Davis)
