A treble of injuries to key men Corey Norman, Danny Wicks and David Gower compounded Arthur's woes.
Playing fullback in the absence of the injured Reece Robinson, Norman went down in the 60th minute with a knee injury that could sideline him for a month.
A standout for Parramatta at both five-eighth and fullback this year, Arthur said the loss of Norman would be a huge blow for the club.
"We'll have to have scans, but I'm not sure," he said.
"They're saying (it's a PCL strain), so that's better than an ACL."
Arthur said prop forward Wicks might have played his last game of the year after hurting his shoulder early in the second half.
"He's been carrying that (injury) for a long time now, it's at the stage where he can't lift it, so he's probably an operation now," he said.
