Arnold said that after Adelaide beat Sydney last month "five or six of their players came and didn’t apologise, but said 'we had balaclavas on tonight and we robbed you'."
Arnie loves stirring the pot. Let's hope, for his sake, Sydney's finishing is a bit more clinical this time.
Why you should watch it
Both teams are desperate to reach a stage they haven't reached for a long time.
Sydney is a big club, but it hasn't been in the grand final since the 2009-2010 season, when it beat Melbourne Victory in the decider. That is much too long a drought for a club of its size.
Adelaide's grand final drought is even longer. It hasn't played in one since the 2008-2009 season, when Victory beat it to claim the prize.
The loser is going to be bitterly disappointed, so the intensity is going to be high. The match is set to be fast-paced and physical, but punctuated with moments of sheer class engineered by the presence of high-class playmakers on either side.
Get ready for a fascinating contest.
What happened last time they played
It was five weeks ago when Adelaide beat Sydney 1-0 in Sydney and what happened that night has been well documented.
Sydney had clearly the better of general play, but a combination of great goalkeeping from Adelaide's Eugene Galekovic and some poor finishing from Sydney saw the result go to the visitor.
Galekovic also had a major hand in the winning goal by deliberately sending a long clearance into space for Awer Mabil, who took possession down the right and cut back into the penalty box before scoring with a left-foot drive in the 82nd minute.
Key battles
Adelaide has again lost the injured Bruce Djite, who is normally a focal point at the front of the attack, so just as it did against Brisbane last weekend it will come at Sydney from a variety of angles and have players pushing into the penalty box down the centre from attacking midfield positions.
Sydney's back four will repeatedly be called upon to make quick decisions on who to pick up among the runners, while the holding midfielders ahead of them have got to either get close enough to put pressure on Marcelo Carrusca and the other playmakers or at least try to block the passing lanes.
Either of Adelaide's central defenders, Osama Malik and Nigel Boogaard, will be on Sydney striker Marc Janko at different times. Janko can play either with his back to goal and control the ball before sending it into the path of a team-mate, or allow the ball to run into his path and shoot.
Malik and Boogaard must maintain a strong physical presence on Janko, but the entire defence has got to keep an eye on him because he will drift away from the centre to try to find space if necessary. It is not unusual for him to bob up unmarked that way and get a free shot at goal.
Why Sydney will win
This season has been a triumph for attacking teams. The best attacking team - Melbourne Victory - is already in the grand final. Sydney FC is the next-best attacking team, with not much difference between the two.
Sydney has a player, in Janko, who can score when it doesn't look like a goal is on, which is a potentially great asset in a knockout match. But it also has others who have contributed strongly in the goal-scoring department recently - most notably Alex Brosque and Bernie Ibini.
Plus, there is another attacking dynamo in Shane Smeltz waiting on the bench.
Why United will win
It has a great record against Sydney, which can be tight in defence sometimes and shaky at other times.
Adelaide will be banking on its possession-based style to open Sydney up with crisp passing and clever running off the ball. There is not what you would you call one dominant goal-scorer in the team, but there are plenty of goal-scorers and it doesn't matter who scores as long as they go in.
Osama Malik is a key player for Adelaide. He is very calm on the ball and capable of starting attacking moves either by running the ball and eventually feeding it to a support player or being right on the money with a 20-metre pass out of the back.
What the players are saying
Sydney's Bernie Ibini said fellow attacker Marc Janko wasn't stressed by his recent scoreless run.
"Marc's the type of guy who is very experienced, so he knows goals will come," Ibini said.
"It's only four games and that's nothing, really. I reckon he's probably saving them for the finals. He knows that sometimes you go a few games without a goal, he knows that. Mentally, he'll be fine."
Adelaide defender Tarek Elrich said he and his teammates weren't getting involved in Sydney coach Graham Arnold's mind games.
"Graham has reminded a lot of people that the last game was apparently a robbery, but at the end of the day we won 1-0," Elrich said. "Not that we’re worrying about him.
"And if we win this game, it’s not going to be about Graham Arnold, it’s going to be about us going into the grand final. For us it’s not worrying about their coach, because their coach is not playing."
What the coaches are saying
Sydney's Graham Arnold loves to try to plant seeds of doubt into the minds of the opposition. On this occasion he suggested Adelaide was worrying about Sydney too much, while Sydney was just worrying about itself.
"They say they don't talk about the opposition, but that's all we're hearing, what Adelaide is saying (about Sydney)," Arnold said.
"And, look, for us, it's about ourselves. I said at the start of the season our biggest opponent is going to be ourselves all year and nothing will change."
Adelaide's Josep Gombau had a bit of a crack at a mind game after last weekend's win over Brisbane, when he suggested his team would be better off than Sydney because it had played a game rather than have the weekend off, but he lost interest in trading shots after that.
"I don’t want to play this (mind) game,” Gombau said when asked to respond to Arnold's suggestion Sydney was robbed the last time it played Adelaide.
"I am a coach, my motivation is not for this. I am a coach that speak on the field."
The villain
Eugene Galekovic is going to have a busy night in goal for Adelaide.
The Sydney attack is not going to be dormant. He may stop everything that comes his way again, but he will certainly be supremely tested by a Sydney forward line that can't believe it went scoreless last time against Adelaide.
If Galekovic puts on another master-class that results in Adelaide going through it will frustrate the hell out of the Sky Blues and their supporters.
The hero
Sydney captain Alex Brosque is a firm favourite among Sydney fans because of his total commitment to the cause on the field and his genial nature off it.
If, in his first year back at the club after playing in the Middle East, he can lead the team back to the grand final it will send Sky Blues fans into raptures. If he were to cap it off with a goal, even better.
The match in numbers
30 - Number of times these two teams have met, for 15 Adelaide wins, 11 to Sydney and four draws.
16 - Clashes in Sydney, where it's seven wins apiece and two draws.
6 - The number of games included in Adelaide's current unbeaten run against Sydney (four wins and two draws). Also the number of wins Adelaide has had in the last 10 clashes. Sydney has won twice and there have been two draws.
4 - Wins Adelaide has recorded in its last five games in Sydney. Sydney won the other one.
0 - Wins Sydney has had against Adelaide this season. Also the number of goals it has scored in the three clashes (0-0 in Adelaide and 3-0 and 1-0 to Adelaide, both times in Sydney).
The verdict
Adelaide's results against Sydney this season read great, but Sydney should have won when it lost 1-0 in the most recent clash. It is rare for a team to dominate a game as clearly as Sydney did on that occasion and get nothing out of it.
Also, when Sydney lost 3-0 to Adelaide on Boxing Day, the Sky Blues were in an injury-ravaged state, having lost several key players for the season. The team was going through a poor run of form and was limping towards the Asian Cup break and January transfer window, when it could re-tool.
Graham Arnold did that superbly, scouring the world for suitable injury replacement players and picking up Mickael Tavares and Jacques Faty. Arnold also made some subtle adjustments to the team's playing style and it came out firing after the break.
This will be a different Sydney team to the one Adelaide has previously met this season. The visitor now faces its biggest challenge.
Adelaide to put up a good fight, but Sydney to win.
