Heading might not exist in football in 10 to 15 years time because of the risks involved, former Tottenham and Hull midfielder Ryan Mason says.
Mason, capped once by England, had to retire from football after fracturing his skull playing for Hull in 2017.
A recent study showed that footballers are three and a half times more likely to suffer from dementia.
“It wouldn’t surprise me in 10 to 15 years if heading wasn’t involved in the game,” Mason, 29, told BBC Sport.
“The research and the momentum it’s getting, I think it’s probably going to open up a lot more stuff that becomes quite shocking.
“I’m not sure footballers are fully aware of the potential damage. This is where the more research, the more understanding, the more education current players get, the better.
“It might even get to a point where you might need to sign something to say that I’m OK [playing with the risk].
“It really is concerning. The problem we have is you don’t know the effects until you get later on in life.”
The Field study, conducted by neuropathologist Dr Willie Stewart, found that footballers were more likely to suffer from dementia and other brain injury diseases, but has not established whether it was caused by concussions from collisions or repeatedly heading the ball.
The family of 1966 World Cup winner Nobby Stiles, who was diagnosed with a brain condition linked to repeated blows to the head, believe heading caused his dementia before he died in October.
Changes have already been made to how often children are allowed to head the ball, but there are also concerns about how head injuries have been treated in football.
Former Tottenham defender Jan Vertonghen said earlier this month that he felt the effects of a concussion for nine months after he tried to play on during a Champions League match two seasons ago.
Mason, who said he was “lucky to be alive” after his clash of heads with former Chelsea defender Gary Cahill, found Vertonghen’s story “quite shocking”.
And he questions why football has opted for trials of permanent concussion substitutions rather than temporary ones seen in rugby union.
From January, teams will be allowed to use two additional permanent substitutes to allow for head injuries. But there has been criticism of that move from Stewart and brain charity Headway, who believe that temporary substitutions are a better alternative.
That process allows a substitute to come on the field immediately, allowing a doctor 10 minutes to make an assessment rather than the permanent option, where the decision is made in a shorter period of time.
The temporary option has flaws, according to Football Association head of medicine Charlotte Cowie, as players can sometimes still be allowed to return to play after a longer assessment.
But Mason, who is now coaching at Tottenham’s academy, says the permanent option adds more “pressure” to the decision.
“Why [is football] not following something that is in place and has worked?” he said.
“Rugby has a protocol in place that gives the players, the team and the individual the opportunity to go off to be tested by an independent doctor away from the pitch where there isn’t pressure from the manager to get the player back on the pitch – or pressure [from the stands] when the fans are back.”