Newcastle have suffered a significant NRL blow with NSW State of Origin front-rower Daniel Saifiti sidelined for up to six weeks with a knee injury.

Saifiti suffered the injury in Sunday’s loss to Parramatta and scans have since confirmed ligament damage to his left posterior cruciate ligament.

At best, it’s hoped the 24-year-old could return within four weeks, with his brother Jacob to start in his spot against South Sydney on Saturday.

Regardless, the injury comes as a hit to the Knights.

Saifiti has enjoyed his best year in the NRL, averaging more than 10 metres per run – the second most of all props in the NRL – and busting 20 tackles.

His combination with David Klemmer is arguably the best in the league, with big games against Melbourne, Wests Tigers and Manly in the next month.