Ajax have admitted to providing “inadequate” on-field medical treatment for Abdelhak Nouri after the former midfielder collapsed during a pre-season friendly last year, the Dutch club’s general manager, Edwin van der Sar, has said.

Nouri suffered a cardiac arrest during the match against the German club Werder Bremen in July 2017 and despite being revived on the pitch and airlifted to a hospital, the 21-year-old suffered “serious and permanent” brain damage.

“We recognise our responsibility and liability for the consequences of this,” Van der Sar said at a news conference. “For a long time we were convinced that Abdelhak had received the best possible care on the field.”

The Dutch club said it had sought an external opinion during the incident and acted accordingly but further investigations showed that a defibrillator should have been used sooner in the treatment.

“Had this happened, it’s possible that Abdelhak would have come out in a better condition,” the former Manchester United goalkeeper added. “This isn’t certain, but it’s a possibility.”

Nouri, born in Amsterdam to parents of Moroccan descent, made 15 appearances for Ajax in his debut 2016-17 season.