In July 2017, at age 20, during a pre-season friendly match, Nouri collapsed and suffered a cardiac arrhythmia attack, which left him with severe and permanent brain damage and unable to continue his career as a footballer.

[5] On 21 September 2016, Nouri made his official first-team debut in a KNVB Cup match against Willem II, and scored a goal.

[7][8] Five days later, however, Ajax reported that Nouri had suffered severe and permanent brain damage as a direct result of the incident,[9] and was in intensive care.

[10] In June 2018, Ajax announced an investigation had found that the medical treatment Nouri received on the field was "inadequate",[11] which prompted a lawsuit from Nouri's family against Ajax through the Royal Dutch Football Association's arbitration panel, who stated a failure to resuscitate him with due haste was responsible for causing his brain damage.

[17] In February 2022, Ajax announced the agreement with Nouri's family included a payment of €7.85 million, that the club would cover all his medical bills, and would retire his number 34 jersey.