Newcastle utility forward Alex McKinnon has fractured his neck and the Knights say it will be several days at least until the full extent of his injury is known.
"His spinal cord is not severed but the doctors are unsure about the level of spinal cord compromise," the club said in a statement on Tuesday.
"It will be a number of days or weeks until the extent of his injury is known."
The club said the 22-year-old has a fracture at the C4 and C5 vertebrae.
McKinnon was stretchered from the field in a neck brace after landing on his head in an awkward tackle by Melbourne forwards Jesse Bromwich, his brother Kenny and Jordan McLean.
The tackle, which happened 30 seconds from halftime of Monday's NRL clash, was put on report by referee Gerard Sutton.
The Storm were also penalised, with Kurt Gidley closing the margin to 18-10 with a penalty goal.
The Knights said McKinnon's family are with him along with club doctor Peter McGeoch.
What should the Warriors do with Dane Nielsen?Related story: (See story)