FIFPro has slammed what they described as "dangerous" playing conditions in Saturday's Club World Cup quarter-final between Western Sydney Wanderers and Cruz Azul in Rabat.
The world players' union also demanded an explanation from soccer's governing body FIFA, the competition organisers, as to why the match went ahead on a waterlogged pitch.
"FIFPro calls on FIFA to clarify why the decision was made to continue this match in these conditions and to ensure that effective rules are in place to prevent a repetition of similar events," said FIFPro director Tijs Tummers.
"The FIFA Club World Cup is one of the most prestigious tournaments in the game, as the winning team deserves the title the best club team in the world," he added.
"Such a competition deserves the highest quality playing conditions, more so, the players as workers have a right to a safe work environment.
"Neither was the case, last Saturday. The players were involved in a match that did no justice to their qualities and aspirations. The conditions were simply dangerous. We are lucky that none of the players suffered a serious injury."
Tuesday's semi-final between Real Madrid and Cruz Azul was moved from Rabat to Marrakech because of the poor state of the pitch at the Prince Moulay Abdellah stadium.
"The whole 120 minutes was disgusting," Wanderers goalkeeper Ante Covic said in a TV interview after the game.
"It was absolutely farcical what happened out there and it's unacceptable to me."
South America champions San Lorenzo will face Oceania champions Auckland City in the second semi-final on Wednesday, also in Marrakech.