Manly are fearing the worst for fullback Brendan Elliot after the 26-year-old sustained a suspected serious knee injury in the Sea Eagles' two-point loss to Newcastle, reports nrl.com.

Des Hasler will be awaiting results from scans on Elliot's knee, with the club expecting a torn anterior cruciate ligament.

Elliot's leg was twisted in a tackle early into the Knights' 26-24 win at McDonald Jones Stadium.

The loss is Manly's third consecutive defeat as they begin to lose their grip on finals contention.

Elliot has been a formidable replacement for the injured Tom Trbojevic, who hasn't featured for Hasler since round six after sustaining a hamstring injury.

The Sea Eagles coach revealed that Trbojevic will remain on the sidelines for another two weeks, while winger Jorge Taufua was a late omission for the Sea Eagles.

"[Taufua] will be back next week. He needed a rest. He'll have time to recover now so he'll be back on deck fresh for next week."

The Sea Eagles will turn their attention to South Sydney this week, as they set their sights on the top eight.

"Equation-wise there's still enough points and there's plenty to be positive about that performance there today," Hasler said.

"The last two weeks we've let four points go," Hasler said referring to the four-point loss against the Warriors at Lottoland.

"So we're making it very difficult … we're walking a tightrope so we need to walk it well."

Hasler was quick to suggest the Sea Eagles were the cause of many setbacks in the loss.

"We shot ourselves in the foot a couple of times with a few disciplinary penalties," He said.