Ajax midfielder Abdelhak Nouri collapsed and was taken to hospital by helicopter during a pre-season friendly against Werder Bremen.
The incident, which happened in the second half of the game in Austria, led to the match being abandoned.
Ajax later said the player was "stable" in hospital and being "kept asleep for optimal treatment".
Nouri, 20, was part of the Ajax squad for the Europa League final against Manchester United in May.
However, the Netherlands youth international played no part in the game, which United won 2-0.
Nouri played a total 15 league and cup games for Ajax in 2016-17, scoring one goal in a Dutch Cup tie.
Former Netherlands captain Ruud Gullit posted on social media: "#abdelhaknouri we pray for you."
Ajax Cape Town, a feeder club for the Dutch side, also sent a message of support.
Latest Stories
-
Driver on bail over fraudulent land transaction
9 minutes -
Common vaginal ‘imbalance’ may be an STI
22 minutes -
Keynote speakers arrive in Paris for Women of Valour
3 hours -
‘Calm down, it’s not over’, Mourinho warns Rangers
4 hours -
It’s time to reset Ghana and private sector must lead the way – Ishmael Yamson
4 hours -
Prosecutors demand Luis Rubiales World Cup kiss retrial
5 hours -
Ghana won’t sink any further, investors must stay – Ishmael Yamson
5 hours -
Dr. Louisa Satekla pays courtesy call on Haruna Iddrisu to promote oral health education
5 hours -
Coastal Civil Society Forum engages tidal wave victims, calls for urgent gov’t action
5 hours -
ECB apologises for Pope Francis Ashes post joke
5 hours -
Denmark postal service to stop delivering letters
6 hours -
Photos: Mahama visits victims of tidal waves destruction in Volta region
6 hours -
Teen armed with gun overpowered by passengers onboard plane
6 hours -
Ghana Month: From war airbase to global gateway – KIA’s evolution and Ghana’s airline struggle
6 hours -
Rosetta Quaicoe: Preventing future Cholera outbreaks in Takoradi: A public health imperative
6 hours