The union for Major League Soccer (MLS) players criticized FIFA, its rules-making body and the league for failing to allow trials of temporary substitutes to replace players suspected of sustaining concussions.

The International Football Association Board (IFAB) said January 18 that no consensus was reached on the proposal for trials by MLS and England's Premier League. The IFAB includes four representatives from FIFA and one each from the governing bodies of England, Scotland, Wales, and Northern Ireland.

"FIFA and IFAB's shortsighted, misguided decision demonstrates once again their failure to prioritize player health and safety in our sport," the Major League Soccer Players Association (MLSPA) said in a statement Friday. "Their refusal to act provides yet another example of global soccer's broken governance structure."

The union maintained current rules "do not provide sufficient time for the proper assessment of players for potential concussions."

"Players too often remain in games with head injuries," the MLSPA said. "Medical professionals also agree that the solution to this problem is to provide for temporary concussion substitutes to allow players to be properly evaluated."

MLS starts its season Saturday, and the union said the league should have adopted a trial without the IFAB's approval.

"The league's lack of courage leaves us with an outdated model that fails to protect players from further injury and allows tradition to triumph over science," the union said. "It is incumbent upon federations and leagues such as the United States Soccer Federation (USSF) and MLS to choose for themselves that the time for change is now. Instead, FIFA, IFAB, the USSF and MLS are knowingly putting players at substantial risk. They each deserve to be held accountable.”

MLS Commissioner Don Garber said Wednesday the league was powerless to act without IFAB approval. He maintained the league was willing to innovate and cited adoption of video review in 2017 as an example.

"I get it. The global game has got to have the same rules and it's not as easy for us just to introduce on our own," he said. "We want them to do it. We'll be the first league to say we'll do it, like we tested video assistant referee (VAR), the first league to do that, and now that's obviously embraced throughout the sporting world. But I'm optimistic and hope."