Major League Soccer are understood to have held talks about potentially being the first league in world football to trial temporary concussion substitutes.

The International Football Association Board last week cleared leagues to hold trials with different methods of concussion substitute but there was initial disappointment that Fifa, the Football Association and the Premier League favoured only an additional permanent substitute.

Neuropathologists, brain injury campaigners and world players’ union FIFpro have all told Telegraph Sport that extra assessment time is needed for medics and that football must urgently introduce the sort of temporary replacement that has been used both in rugby and which allows at least 10 minutes for a more detailed off-field diagnosis.

Sources have also since told Telegraph Sport that MLS have held discussions about introducing a model that would give medics an additional window of time before having to decide whether a player is permanently removed.

IFAB hope that there will be a range of different trials in leagues around the world which could then inform a potential rule change next year.