World players' union FIFPRO says it is "surprised and disappointed" that no concussion trial protocols have been agreed yet.

The union had hoped that a variety of head injury protocols would be tested in various competitions around the world in the 2020-21 season after the game's law-making body, the International Football Association Board, agreed in principle to trials taking place back in February.

However, IFAB has said is still in discussion with experts over what the protocol or protocols will look like, and only at that point would competitions such as the Premier League be able to apply to try one out.

FIFPRO has expressed its concern over the delay and said: "FIFPRO is surprised and disappointed by reports that there are no plans to trial improved concussion protocol, including temporary substitutes, during the forthcoming professional football season.

"In order to safeguard professional footballers the existing protocol has to be brought up to date with other sports as soon as possible. We urge stakeholders to address this matter urgently and make the health and safety of players a priority in the game."

Currently medics have three minutes to assess a player with a suspected concussion and must then either substitute him or leave him on the pitch.

World governing body FIFA favours a continuation of the three-minute assessment but with additional substitutes being available if a player is suspected to have concussion.

It hoped to trial this at the Olympic Games in Tokyo, but that event has now been delayed until next summer because of the coronavirus pandemic.

Football Association chief executive Mark Bullingham said this was also his favoured approach when he spoke about it in February.

FIFPRO's preferred approach would be to increase the length of the assessment period to 10 minutes, with a temporary substitute introduced while the assessment takes place.

At the end of the assessment the team medic must decide whether the injured player can stay on or must come off.