Premier League: What are the rules on concussion and substitutes?

Once a referee stops a game for a suspected head injury, a doctor or physiotherapist will assess the player on the pitch.

The player then must leave the field of play for more medical assessment and stay off for at least 30 seconds after the game restarts. If it is judged that the player could be concussed, they must not return to activity for at least 24 hours.

Medical assessments can include looking for visible signs of concussion like a vacant stare or confusion, as well as the player reporting symptoms like dizziness or a headache to the medics.

The ‘concussion recognition tool’ also includes a series of questions medics can ask the player – such as, what time of day is it? – to assess their brain function.

Premier League teams are permitted to make one ‘concussion substitution’ per match, which do not count against their usual substitution limits.

If judged to be concussed, the player should be supervised for 24 hours and begin a six-stage ‘return to play’ process. This starts with an initial 48-hour period of rest with minimal physical and ‘cognitive’ activities, such as working and using screens.

The FA then recommends “a staged and graduated return to full daily activities”, where “football training is allowed, but at a rate that does not worsen existing symptoms more than mildly or produce new symptoms”.

The second stage allows light exercise, followed by the final four stages of football-specific exercise, non-contact training, full-contact training, and finally a full return to play.

This article is the latest from BBC Sport’s Ask Me Anything team.