The Wanderers, who've battled to just one win in 16 domestic outings this season, kicked off their ACL title defence with a 3-1 victory over Japanese giant Kashima Antlers on Wednesday.
The win was just the moral boost they desperately needed before hosting an in-form Sky Blues side at Parramatta Stadium on Saturday.
But while applauding Western Sydney's triumph, Arnold said its change of fortunes was down to the slower style played in Asia.
"They continue to represent Australia brilliantly," the Sydney FC mentor said ahead of training on Thursday.
"But I think it shows the ACL is a much slower game than the A-League.
"The A-League is a lot more about the quick transition. Teams defend with six and attack with four.
"I watched last night's game and you do have to give full credit to the Wanderers - they were fantastic."
The Wanderers arrive on Friday morning with less than 24 hours to prepare for the derby.
They'll be without striker Brendon Santalab, who suffered what's suspected to be a season-ending shoulder injury in a 2-1 loss to Adelaide United last weekend and Shannon Cole, who injured his shoulder in Wednesday's ACL victory.
The extent of both injuries is expected to be known by Friday.
But coach Tony Popovic won't be lacking fresh legs having left key players like goalkeeper Ante Covic, Iacopo La Rocca, Brendan Hamill, Romeo Castelen and Nikita Rukavytsya out of the trip to Japan.
"I don't think the travel will take much out of them," Arnold said.
"Tony left five very good players behind so we're expecting a very tough game as normal."
The Sky Blues come into Saturday's match fresh off a 4-2 thumping of Central Coast Mariners last week.
Arnold left the match unhappy however, berating his side's poor defending.
The Sky Blues mentor says with their attack clearly firing, having scored 15 goals in their last four outings, he's focused all his attention of defence this week.
"We're in great form, we're scoring a lot of goals and no doubt the other teams will be fearing our attack," he said.
"We've got to tighten up our defence, we were poor in that area last week.
"We worked on that on Tuesday and we'll work on that again today so we'll be ready for Saturday."
