Pearce left the field late in the second half and Newcastle coach Nathan Brown admitted afterwards: “It’s not great.”

It’s understood the best-case scenario is that Pearce will be out for three months, but if he needs surgery he may not play again this season.

Pearce's setback means NSW coach Brad Fittler will be forced to pick a new halfback for this year's State of Origin series.

The interstate series begins on June 6 and ends on July 11.

Pearce's injury comes a month after rookie candidate Nathan Cleary went down with a knee injury that initially ruled him out until round 13 - the week after the Blues go into camp for game one.

The probable unavailability of both Pearce and Cleary significantly whittles down the list of possible options to partner likely five-eighth James Maloney.

Luke Keary has been in strong form for the Sydney Roosters, while Wests Tigers No.7 Luke Brooks has also recently been tossed up as a possibility to make his Origin debut.

Other candidates include South Sydney playmaker Adam Reynolds and Cronulla link-man Matt Moylan, both of whom have previously pulled on the Blues jumper.

Brown said Pearce, who has been the NSW halfback for six of the past eight years, was in good spirits after the match in Tamworth despite his NRL season being dashed.

"It's not great," Brown said after Saturday’s win.

"He is disappointed. Mitch loves playing. Game day is his favourite day of the week. They are the types of players you want in your club. Whatever the result is he will still contribute while he is not playing."

Pearce's injury also means Brown could be forced into recalling Brock Lamb, who was dropped in favour of Jack Cogger on Saturday, for next week's clash against Manly.

First-choice five-eighth Connor Watson is a chance of returning early from a shoulder injury.

"We've got Connor coming back next week, Brock played reserve grade today, (Jamie Buhrer) filled in today and did a good job in the last six or seven minutes, and came up with the kick," he said.

"We've got to go into the Manly game full of confidence, that's what we've got to do."