Yet, football never fails to surprise. Arsene Wenger's side have earned 22 out of 24 possible points since that woeful defeat, making a clear statement of intent that they are indeed title contenders this season.
So what's changed since the opening day of the season? Call it the "Mesut Ozil effect" or Arsene Wenger's shrewd management, but Arsenal's form has been down to the individual improvement of nearly every player in the starting XI.
Hence, keep in mind that I've decided to only include three players, as it would be rather pointless to rattle on about almost every player in the squad.
Here are Arsenal's three most improved players based on their performances this season compared to their performances last season.
All statistics via WhoScored.com.
There have been countless Arsenal players who have stepped up their games this season, so below are those who just miss out.
Szczesny has enjoyed an excellent start of the season, especially when compared to his complacent performances last season. The Pole finally finally seems to be living up to the potential he displayed in his debut campaign back in 2010-11, and it very likely has to do with the competition for the No.1 spot with Lukasz Fabianski and Emiliano Viviano patiently waiting in the wings.
The only reason Mertesacker doesn't make the top three is that his performances last season were actually quite impressive as well. He's taken another step up, though, becoming a leader as he wore the captain's armband earlier on this season. The big German has evolved into one of the Premier League's most solid centre-backs, making up for his lack of pace with his exceptional anticipation and reading of the game.
Like Mertesacker, Gibbs just misses out on the top three because he was playing excellent football last season; however, he's clearly matured even more and has asserted himself as the first-choice left-back ahead of Spanish international Nacho Monreal. Defending strongly and frequently charging forward with intent, Kieran Gibbs is quietly becoming one of the best left-backs in the Premier League.
After two leg breaks and a rather disappointing 2012-13 campaign, Bacary Sagna is beginning to look like his old self again.
The Frenchman has been one of Arsenal's most consistent players this season, playing in almost every single one of Arsenal's matches and doing his job competently, even serving as a makeshift centre-back on a few occasions.
Although he doesn't get forward quite as often as he used to, his trademark early crosses can still be seen week in and week out, and he's as solid as ever in defense.
While his contract expires this summer, there's no reason why the club shouldn't consider offering the 30-year-old an extension.
Sign him up, Arsene!
Already scoring eight goals in all competitions this season, Olivier Giroud has stepped up as Arsenal's clear first-choice striker and is a far cry from the Giroud of last season.
Although his haul of 17 goals in 2012-13 was respectable, he's clearly improved in every aspect of his game: He holds up the ball more often, finishes his chances more clinically and plays with an overall confidence he didn't seem to have last season.
It's incredible to think that Giroud was playing Ligue 2 football in France just a few years ago, and now he's a serious contender for this season's top scorer in the Premier League.
Aaron Ramsey's unprecedented spectacular form for Arsenal has arguably been the surprise of the season so far.
The Welshman is the Gunners' top scorer on nine goals, scoring everything from Messi-esque runs to cracking volleys. The goals are really just a bonus. though: Ramsey averages 4.4 tackles per game, which is the fourth-highest rate in the Premier League, and completes 71.9 passes per game—more than the likes of Steven Gerrard and teammate Mesut Ozil.
Nicknamed "Rambo," the 22-year-old has completely turned around his career, playing his football full of confidence, whereas just a year ago he was the subject of harsh criticism by Arsenal supporters.
If Arsenal really are to challenge for the title this season, there's no doubt Aaron Ramsey will be key to the Gunners' success.