Leeuwin was hit by a man on a scooter at 30mph outside the Eredivisie club's training ground, near to their Galgenwaard stadium.
But incredibly, according to Dutch newspaper Telegraaf, Leeuwin's team-mates managed to chase down the offender and pinned him to the ground before the emergency services arrived.
The 29-year-old defender Leeuwin – who made 35 appearances last season – was lifted into an ambulance, and a helicopter was also called.
Leeuwin was taken to the University Medical Center Utrecht for treatment but no further details about his condition were provided.
Depending on the seriousness of his condition, Leeuwin could be set to miss the start of the new Eredivisie season which commences on August 11.
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