It is believed Dragons prop Korbin Sims played out the first half of Sunday's win over the Knights with a fractured arm.
The 27-year-old, playing his second game as a Dragon after crossing from the Broncos over the summer, is thought to have sustained the injury in the 25th minute of the Dragons' 13-12 win before remarkably staying on the field until half-time.
Dragons coach Paul McGregor said a half-time evaluation revealed the extent of Sims' injury.
"We’re not having too much luck there. It looks like he’s broke his arm," McGregor told NRL.com.
"Coming from our medical staff, they weren’t sure how bad it was and certainly Korbin was displaying to the medical staff that he’d like to stay there and try to work through it.
"Then at half-time, the doctor had a look at it … and the choice was made that he’s not to return to the field.
"We still don’t know if it’s broken by the way – it could be a bad cork – but he’s broke one in the past and he’s had that strapped before the game."
The Dragons play host to the Bulldogs on Sunday.