New York Islanders centre John Tavares left Saturday's game against Dallas with what the team is calling a mild concussion.
The sophomore was elbowed by Adam Burish of the Stars late in the first period.
The team said he would be evaluated on Monday.
Tavares, who was selected first overall to much fanfare in the 2009 NHL draft, had 24 goals and 30 assists last season.
"He's arguably our best forward, and John's a prolific player that brings a lot of offence to our team," captain Doug Weight said on the Islanders' official website.
"Each day, every team goes through things like this, and I think we responded well. Hopefully, he's back sooner than later. I think he's doing pretty good."
New York continues to be hammered by injuries, having lost defenders Mark Streit and Kyle Okposo in the pre-season.