"Amrabat is a warrior," coach Herve Renard told reporters. "He wanted to play... I was lucky to have a player like this.
Morocco lost 1-0 against Portugal to become the first side to be eliminated from the tournament. They lost their opening match against Iran by the same score.
Amrabat spent a night in hospital after a 72nd-minute clash of heads with Iran's Vahid Amiri in St Petersburg on Friday.
Morocco's medical team were criticised for slapping the player, who appeared to be unsteady on his legs, around the face as they treated him on the sidelines. The Royal Moroccan Football Federation later said Amrabat would be unavailable for a week.
The Watford player, however, began against Portugal at the Luzhniki Stadium wearing a protective head guard, only to rip it off and throw it away 16 minutes into the game. World players' union FIFPro said in a statement: "This is yet another alarming example of a player being put in harm's way. Amrabat returned to action too soon according to medical guidelines.
"Four years on from the debacle of the last World Cup, where several players did not receive adequate care, football has not made sufficient progress in concussion management. Repeated calls to implement world-class safety standards have been overlooked."
Former Ireland international Kevin Kilbane also criticised football's approach towards concussion.
"We have to be careful of course, we don't know what discussions he's been having with his medical team," he told the BBC. "But within football we've got the mentality in many respects of turning a blind eye to concussion. We have to learn from other sports. We have to learn from rugby. We have to learn."
In rugby union players who suffer a blow to the head must be replaced for 10 minutes for a head injury assessment (HIA) to be carried out. Players with confirmed concussion cannot return to the pitch and are monitored by medical staff before being allowed to start playing the sport again.
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)