NIJMEGEN, Netherlands (AP) -- American forward Jozy Altidore sustained a head and back injury in AZ Alkmaar's 1-1 tie at NEC Nijmegen on Wednesday.
Altidore clashed with NEC defender Pavel Cmovs in the 29th minute and was knocked unconscious on the sidelines.
Altidore, AZ's top scorer with 15 league goals and 19 overall, returned to play for only two minutes. He was replaced by Ruud Boymans, who went on to score in the 59th.
The extent of Altidore's injury couldn't be ascertained.
The Americans play Scotland, Brazil and Canada in exhibition games ahead of the start of World Cup qualifying next month.