Premier League clubs and head injury charities have expressed concern after Tottenham refused to rule out playing Hugo Lloris in the Europa League on Thursday four days after he was knocked unconscious against Everton.

Fifa guidelines suggest there should be a five-day gap after suffering concussion before someone can play again. However, Tottenham say they will assess Lloris's condition on Wednesday to determine his availability for the Europa League home tie against Sheriff.

Declan Lynch, Arsenal's first-team physiotherapist, said he would never take a risk with a player's health by ignoring Fifa's guidelines. "Simple answer, no," he said. A fortnight ago Matthieu Flamini was ruled out of Arsenal's Champions League home game against Borussia Dortmund after being concussed against Norwich. Lynch, who was head physio at London Irish before joining Arsenal, said his experiences in rugby union had made him cautious with head injuries.

"I've worked in rugby so I've been exposed to a lot of concussion," he told the Elite Minds in Sports Analytics summit. "It's not an area I would mess with."

Everton's head of sports science, Steve Tashjian, said he would be wary of bringing a player back from a head injury after four days. "I come from the States and we have a much different perspective on treating concussions," he said. "If the Lloris situation happened in the States there would be a significant length of time away depending on how the tests came out."

Spurs have argued that Lloris was assessed on the pitch by the club's medical team and given the go-ahead to continue and that a precautionary CT scan after the match showed no ill effects. However, the brain injury charity Headway warned there is a chance that Lloris could pick up a secondary injury if he plays on Thursday.

"We are very concerned about this," said its spokesman, Luke Griggs. "Some of the damage following a traumatic brain injury, however mild, might not be picked up on scans. It sometimes take time for the symptoms to come through.

"If there is a slight swelling to the brain it might be that a secondary knock in Thursday's game might exacerbate the problem. You need to allow the brain to fully rest and recover."

Headway has also called for football to introduce independent specialists to pass a player fit following a concussion, rather than leaving it to club doctors.

"The situation on Sunday was farcical with the player and manager appearing to overrule the medical staff," said Griggs. "If a player is knocked unconscious in a contact sport he should not be playing for a couple of weeks.

"The player was knocked unconscious for a period of time, so there needs to be a safety-first approach to ensure there is no long-term damage to the brain."

Brad Friedel, who warmed up to replace Lloris at Goodison Park, said his team-mate was OK after the collision with the striker Romelu Lukaku. Friedel told Sky Sports News: "He's fine, all goalkeepers have had those kind of knocks. He's fine."

The Premier League's expert group of doctors are expected to discuss the issue of concussion and head injuries at their next meeting, following a spate of incidents involving players including Lukaku, Mathieu Flamini and Andros Townsend.