Newcastle skipper Kalyn Ponga was ruled out of his side's NRL match against the Wests Tigers after sustaining a head knock less than 90 seconds into Sunday's game.
The five-eighth, who took an extended break at the end of last season due to repeated concussions, lay prone after attempting to make a tackle on Tigers forward Asu Kepaoa.
Ponga has suffered four concussions in the past 10 months.
He was also ordered off by the NRL's independent doctor in the Knights' opening round loss to the Warriors but was later cleared.
The fullback did not return to the field at Leichhardt Oval on Sunday.
Newcastle's woes were compounded when hooker Blayke Brailey failed a head injury assessment midway through the second half.
Despite also seeing winger Dominic Young go to the sin bin for a professional foul, Newcastle were able to hold onto a 10-6 at the halftime break.
