Mezei, who was hospitalized on Sunday, will spend the next three days at the Cleveland Clinic under observation because of blood behind his left eye. Mezei has been unable to open the eye after receiving several stitches.
"He's not out of the woods yet," Panthers general manager/coach Rick Dudley told the Ft. Lauderdale Sun-Sentinel . "We won't be able to get a real accurate prognosis until it settles down a bit."
Mezei was struck by a slap shot from Capitals forward Jeff Halpern during Florida's 3-2 win.
After missing 70 games last year after breaking his foot twice, Mezei has four assists in 22 contests for the Panthers this season.
"He's getting some freaky injuries," Dudley added. "But I've seen it happen like this a lot of times where you get all sorts of freaky injuries and then go nine years without anything. Hopefully this will be the case."
Meanwhile, Panthers forward Eric Messier will miss at least a month with a dislocated wrist sustained on his first shift Friday against Atlanta.
Forward Mikael Samuelsson will also miss at least a week with a broken jaw suffered when he was hit by Mezei's stick against Atlanta.