A potential season ending knee injury to Newcastle co-captain Jamie Buhrer further soured Saturday night's 18-16 defeat against the Sydney Roosters.

Buhrer left the field in the 27th minute, leaving the Knights a player down for the rest of the match.

Scans are expected to confirm the back-rower has ruptured his ACL, ruling him out for the remainder of 2018.

Buhrer also did the same injury while on the books of the Sea Eagles in 2014 and 2015.

Despite the long-term recovery, coach Nathan Brown has backed Buhrer to bounce back.

"Throughout his career he has had a few bad injuries, but he has always seemed to bounce his way back," Brown said.

"He's disappointed, as is the case when one gets those long season ending injuries.

"Obviously he is getting into the latter part of his career, so he is not a young bloke – but he'll be right and bounce back in rehab.

"I'm sure he will get back on the field next year and play some good footy – he has seemed to get over it every other time, so I am sure he'll bounce back again."

Buhrer's injury adds to a list that seems to be growing each week.

Currently sidelined are halfback Mitchell Pearce, Nathan Ross, Brock Lamb, Tautau Moga, as well as Daniel and Jacob Saifiti – while several others have missed games week to week through injury.

Knights hooker Danny Levi. ©Paul Barkley/NRL Photos

Despite his team's fourth loss in five matches, Brown is remaining positive.

"The key thing was our effort tonight and we competed hard against a side that has a roster with very talented players in it," Brown said.

"If you really be truthful, it was a couple of plays from Test players, or Origin players.

"Latrell (Mitchell) did it against Queensland the other night and he did it to us tonight, and Fergie (Blake Ferguson) is a Test player, and when you have them in your roster, that's what they are there for.

"We let ourselves down in key moments, which is to be expected when you look at the experience of our halves compared to theirs, but as a whole, the effort was super and we hung in the contest."

Co-captain Aidan Guerra admits that while the result was disappointing, the players have come a long way and learnt valuable lessons, which are starting to show on the field.

"There was a few key moments there where you could just see the commitment shown by each other, and that's what we are starting to appreciate," he said.

"Appreciate that those moments in a game really count, and I think for us to come up with those big moments, kept us in the fight (tonight).

"Although we didn't get the result, we built on last week, and the effort, you can't fault it."