The American striker slammed his head against the pitch's ad boards, before walking off the field under his own power.
Altidore was battling for the ball with NEC's Pavel Cmovs when he slipped on the wet pitch and fell into the ad boards, hitting his head. The striker was down on the pitch for a minute before he was able to slowly walk off.
AZ went on to draw the match 1-1, falling into fifth in the Eredivisie and out of any European position. The team will finish its season Sunday against Groningen.
Following the injury, AZ press officer delivered some good news to MLSsoccer.com, saying "He has a big bruise on his back, and that's actually all. It means he is doubtful for Sunday."
On Twitter, Altidore wrote: "Thanks for all the support from you guys. Very painful accident but ill be ok and ready for the weekend if called upon by the manager."
Altidore has scored 15 goals in the league and 19 total this season, making it by far his most successful campaign in Europe. The 22 year-old is slated to join the U.S. national team in two weeks, as it prepares for friendlies against Scotland, Brazil and Canada, followed by the beginning of World Cup qualification.
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