Daley Blind's heart defibrillator goes off during Ajax match

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Promes leads the way as Ajax cruise past Wolfsberger (1:02)

Quincy Promes and Ryan Gravenberch guide Ajax to a 2-0 preseason victory in Austria. (1:02)

Ajax Amsterdam defender Daley Blind had to be substituted during a preseason warm-up match against Hertha Berlin on Tuesday when his implanted heart defibrillator went off.

Blind was diagnosed with heart muscle inflammation after suffering from dizziness during Ajax's Champions League match against Valencia in December. The ex-Manchester United player was subsequently fitted with a Implantable Cardioverter Defibrillator, or ICD, and returned to full training in February.

Blind sat down when the device went off but was able to walk off the pitch to be substituted in the 79th minute on Tuesday's game.

"He has no symptoms. The ICD went off and right after that he was fine,'' Ajax coach Erik ten Hag told Ziggo Sport. "We'll do some tests and wait for the results and then make decisions,'' he added.

Ajax won the match at the Johan Cruyff Arena 1-0.

The Associated Press contributed to this report.