Doctors have admitted Antonio Puerta's progress in hospital has been 'unfavourable'.
The Sevilla wing-back is in intensive care after suffering a heart attack during his team's victory over Getafe at the weekend.
He collapsed on the pitch, and again in the changing rooms, before being rushed to hospital after being given cardiac resuscitation.
Puerta's condition remains 'very critical' after doctors at the Virgen del Rocio hospital in Seville provided an update on Tuesday.
"The player remains in the hospital in a very critical state and his progress is unfavourable," said doctors.
"The condition of patient Antonio Puerta is not favourable due to the progression of the postanoxic brain injury and the multiple organic dysfunction caused by the prolonged cardiac arrest that led to his admission to hospital."
Meanwhile, Puerta's former Sevilla team-mate Jose Antonio Reyes revealed his hope that the Spain international will pull through.
Reyes - now at Atletico Madrid - has visited Puerta in hospital and admits he is 'distraught' by his old colleague's condition.
"I have experienced many moments with him and at this time I have a bitter taste in my mouth," said Reyes.
"He is strong and I am certain that he will come out of this. This is what we all hope for.
"I am distraught because when something like this happens to a team-mate it is very hard."