Alexandre Lacazette scored on his first outing in an Arsenal shirt.
Lacazette, a 68th minute substitute, scored in the 83rd minute and Arsenal’s £52m record signing got a huge cheer.
Per Mertesacker opened the scoring after four minutes and Arsenal made ten substitutes after 68 minutes to give everyone a work-out.
The score would have been higher but for Sydney keeper Andrew Redmayne - an Arsenal fan who had a two week trial at Arsenal - who made a string of great saves, including one from Danny Welbeck’s second half penalty.
Here's five things we learned:
1. Per Mertesacker has been reborn
After his heroics in the FA Cup final, is there no end to his super powers?
Sure enough, Per Mertesacker hooked home the opener after just four minutes.
He looked assured at the back, looked sharp and showed a sharp burst of pace on more than one occasion.
He is determined not to think too much about his role with the academy at the end of the season because there is a whole year of playing ahead. And he looks determined to seize the moment.
2. Arsenal’s kids are alright
Arsenal started with four youngsters in their line-up but one really caught the eye.
Reiss Nelson, 17, known as a winger, played as a right wing back and was outstanding with his pace, movement, dribbling and runs.
He is seen as Arsenal’s best prospect in his age group - and no wonder. He really is one to watch.
Cohen Bramall has fabulous pace and flew down the left. The jury is out as to whether he will make it.
Joe Willock looked bright in midfield and Krystian Bielik solid if a little clumsy with his passing.
3. Walcott has much to prove
Theo Walcott has a bit to prove this season after losing his place in the run-in, especially when Arsenal switched to a 3-4-2-1 system. That formation does not really allow for natural wingers.
Walcott played as one of the two behind the striker, he looked pacy and eager to get involved.
It is clear Walcott has a new role and a challenge ahead to win back his place in the starting line-up. And he looks in the mood to do it.
4. Arsenal are a big draw
The ANZ Stadium looked an 80,000 sell-out and whipped up one hell of an atmosphere with pre-match fireworks, a sense of excitement and anticipation and it felt like a huge occasion.
Talking to the locals, they reckon Liverpool, Manchester United and then Arsenal are the big boys Down Under.
Arsenal have laid on local events, coaching clinics, the fans really got into the mood and wore their colours. This charm offensive is working so well.
5. What did the game tell us?
Arsenal are definitely sticking with the new 3-4-2-1 system.
Some players look sharper than others. Francis Coquelin looked quicker and in the zone. Danny Welbeck needs to sharpen up. Mesut Ozil is a joy to watch and his passing against weaker opposition looks even more brilliant.
There was an amusing moment when Walcott’s shot was blocked by Sebastian Ryall. The ref gave a penalty for handball, the giant TV screens showed it hit his back and they quickly stopped showing the replays. Too late, the ref couldn’t change his mind but Welbeck missed anyway.
Arsene Wenger only made one substitution at half time - Emiliano Martinez for Petr Cech - which suggests that the 25 man squad has been split into two. One lot play more minutes in this one and the others on Saturday. Wenger brought on TEN subs in the 68th minute, the most exciting of all was Alexandre Lacazette for his first outing in an Arsenal shirt.
Finally, if it had not been for Sydney’s Andrew Redmayne then Arsenal would have won very comfortably. Redmayne had a two week trial with Arsenal, is an Arsenal fan and enjoyed having the game of his life.
Player ratings
Cech 6 (Martinez, 46, 6)
Bielik 6
Mertesacker 7
Kolasinac 7
Nelson 8
Coquelin 7
Willock 7
Bramall 6
Ozil 7
Walcott 6
Welbeck 6
Ten subs in the 68th minute: Lacazette, Giroud, Oxlade-Chamberlain, Iwobi, Monreal, Xhaka, Maitland-Niles, Elneny, Malen, Nketiah.