Campbell-Gillard ought to have been celebrating his 200th NRL game on Sunday but his milestone match was muted following his brother's death.
Arthur said his side, which finished 28-24 winners in front of 20,354 at CommBank Stadium, wanted to honour a selfless and committed teammate with a victory.
All of Parramatta's players wore black armbands.
"We were playing for 'Reg', he's shown plenty of resilience the last couple of seasons and he's had a lot of things not go his way on the field," Arthur said.
"He always puts his teammates first and today, we needed to put him first.
"It's been tough, (the loss of) his mother and then his brother but he has never shied away from his responsibility for the team.
"We needed to repay him today."
Things, though, didn't get off to an ideal start for Parramatta.
Manly sliced through the Eels' defence with ease to take a 14-0 lead inside the opening 20 minutes courtesy of tries from Reuben Garrick and Jaxson Paulo.
Jaxson Paulo's try helped get Manly out to a 14-0 lead over Parramatta. (Mark Evans/AAP PHOTOS)
The Eels needed a spark and they got it from Junior Paulo, the big Samoan prop blasting through the Manly middle and offloading at will after being thrown on from the bench.
Paulo set up Mitchell Moses soon after Will Penisini had scored the Eels' first try and added a vital punch from the interchange bench.
"I'm really happy how Junior is playing, and for the group, because of his attitude," Arthur said.
"He wants to start but he'll do what's best for the team.
Junior Paulo was immense for the Eels. (Brendon Thorne/AAP PHOTOS)
"He changes the course of the game for us and he's done that two weeks in a row. He could've kicked stones, but he hasn't, he's been a great leader."
Manly showed some signs of life but they couldn't get a stranglehold back on the game after letting their dominant start slip.
Kelma Tuilagi and debutant Blaize Talagi further extended the Eels' lead after halftime.
Trailing 26-18, the Sea Eagles were denied a try with a quarter of an hour to go after the bunker ruled Eels back-rower Luca Moretti was obstructed by Jake Trbojevic.
The Manly lock barely made contact with Moretti, but the slight coming-together opened up a hole for Tom Trbojevic to race through.
"I don't think he was going to get there, but he played to the rules," smiled Manly skipper Daly Cherry-Evans.
Manly coach Anthony Seibold refused to blame the obstruction call for the loss and would be privately filthy at how his side blew a 14-0 start away from home.
"It's a tough comp, everyone has seen the results," said Seibold.
"There's a cluster of teams that are really close and Parramatta were too good today, at times.
"But there's certainly some things that we can hang onto and keep growing off the back of that."
Josh Aloiai was sinbinned late in the match for throwing a punch and could be at risk of getting suspended for next week's clash with St George Illawarra.
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