Parramatta's premiership tilt has taken a further blow, with fears hooker Reed Mahoney has suffered a season-ending shoulder injury.

The Eels looked hapless in their 40-12 defeat to the Rabbitohs on Friday night, a loss that now places Brad Arthur's side six points behind the third-placed Panthers with an extra game played.

Parramatta could also find themselves as low as sixth by the week's end should the Roosters and Sea Eagles manage upsets over Penrith and Melbourne respectively.

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Their positional conundrum isn't the only worry on Arthur's mind in the aftermath of Friday's defeat to the Bunnies, with the Eels now sweating on the results of Mahoney's diagnosis.

An awkward landing amid an attempted tackle on Souths star Latrell Mitchell left Mahoney in tears as the Parramatta dummy-half made his way back to the rooms.

Initial signs suggest Mahoney will likely go under the knife, requiring further attention to the shoulder he damaged earlier this season.

Speaking post-game, Arthur expressed his fear and sorrow for his star rake.

"It could be the end of him for the year," he said.

The Eels will be hoping to snap their three-game losing streak next Saturday as they face Manly, with games against the Cowboys, Storm and Panthers to follow in what will be a tough run home for Arthur's side.

Parramatta are already without gun forward Reagan Campbell-Gillard for the next month with a groin injury, while Blake Ferguson (calf), Wiremu Greig (ankle) and Oregon Kaufusi (head knock) are also battling in the casualty ward.