Ajax coach Marcel Keizer says Abdelhak Nouri appeared completely fit after a medical just a week before he suffered a cardiac arrhythmia during a friendly on Saturday.
The 20-year-old had to be resuscitated on the field and taken to hospital by helicopter after he collapsed off the ball in the game against Werder Bremen in Austria.
Ajax later confirmed the player was stable and had a heartbeat but was being kept asleep in hospital.
Keizer says Nouri had been shown to be completely fit and the first tests on his heart after his collapse have returned positive results, but the club are currently awaiting brain scans on the highly-rated midfielder.
"He was 100 percent fit," Keizer told AT5. "We are waiting on the results of the neurological tests. The results could come on Tuesday. He is in good hands and is being well cared for.
"Now we hope, it's an important result for us. Everyone is feeling tense. Our doctor stayed there to keep in contact with the hospital.
"His family is there, they get all the updates first and then we hear it. I tried to distract myself on Sunday but just got on my bike. I tried to occupy my mind, but it didn't work."
Keizer coached Nouri in the Jong Ajax side last season, with creative attacking midfielder scoring 10 goals as they finished runners-up in Dutch football's second tier.
Nouri, affectionately known as Appie, has been with Ajax since he was seven years old and the new senior coach says the incident has devastated the entire club.
"It did not matter if the players came to training or not, everyone loves Appie. We encourage everyone to talk about it, cry together," he said.
"He has a very good relationship with his room-mate Hakim Ziyech. But there are guys who have played football with him for 12 years. It's not easy.
"I just hope he gets better. He represents Ajax for me, dominant and attractive football. That's Appie.
"We are not so concerned with the qualifying round of the Champions League, it's all about Appie first."