Newcastle Knights players had been discussing at the weekend how centre Tautau Moga appeared to have overcome his horrific run with injuries but less than 24 hours later they were fearing his career was over.

A "devastated" Moga suffered his fourth anterior cruciate ligament injury while scoring the opening try in the Knights 30-12 loss to the St George Illawarra Dragons at WIN Stadium on Sunday.

The 24-year-old now faces an uncertain future.

Moga ruptured his right ACL twice in eight months with the Sydney Roosters and for a third time when he was with the North Queensland Cowboys in 2015. But he made a successful return to the NRL last season for the Brisbane Broncos.

In just his fourth match since joining the Newcastle Knights, Moga has now ruptured his left ACL. The three previous operations were on his right knee.

"He's buggered; he's done his cruciate unfortunately so it's a bad day all round for us," Knights coach Nathan Brown said.

"It's certainly not a good thing for anyone. Just more disappointed for Tau because he's been through three before.

Match Highlights: Dragons v Knights - Round 4; 2018

"He's gone through two years of playing consistently and against Canberra he was starting to show for us what he was going to be, and when he started the game today he was outstanding.

"You feel for him and his partner, his little one and his family because they are serious injuries. These are a part of the game and we have to deal with them as best as we can."

Co-captain Mitchell Pearce revealed teammates were only the night before discussing how Moga had overcome run of bad luck and how pleasing it was to have him in the side.