The year before, the two clubs collided over the move for Cesc Fabregas and it was a long and very public affair that made any negotiations between the sides in the near future seem unlikely.
Song spent six years in London and Arsene Wenger nurtured the player from the age of 17. The patience of supporters and managers alike isn't always afforded to youngsters trying to prove their worth at the bigger clubs.
His final season at the Emirates was the catalyst for the deal, as he registered 13 assists after averaging only two in his previous campaigns.
The chipped through ball to Robin van Persie became something of a trademark, with the striker praising Song after he assisted the winning goal against Liverpool.
"It was the same pass from the same guy, Alex, an unbelievable pass," Van Persie told Sky Sports (h/t Arseblog) after the match. "Alex is a really good player, he can see it and actually do it."
His passing range was clearly underrated, whilst his ability to sit in front of the back four and break up the play was missed deeply by Arsenal the following year.
With two years left on his contract, £15 million was a decent return for a holding midfielder and there was every chance he wouldn't be able to recreate his assist record with Van Persie also leaving the club.
At Barcelona, the bemusement stemmed from the fact that they already had two of the top defensive midfielders in world football.
Sergio Busquets was immense and Javier Mascherano had been forced to move back to the centre of defence in order to get regular game time. Song was effectively going to be third choice if he was deployed at the base of a midfield three, but was that the reason he was brought to the Camp Nou?
When Seydou Keita left Barcelona, they lacked a physical midfield presence that was needed for certain matches. Song was that answer, as he was mobile enough to provide a box-to-box threat.
With Xavi, Andres Iniesta, Thiago and Fabregas as the other options further forward, though, once again it was going to be an uphill battle.
A month after he joined, things made a little more sense, as he was used as a centre-back in the Champions League against Spartak Moscow.
Tito Vilanova chose him ahead of youngster Marc Bartra, as the coach admitted to FCBarcelona.com that Song "was brought in for this purpose and he has more experience."
"Song is a player that brings the ball out well from the back because he’s played in the pivot position many times before," Vilanova explained further.
Overall, his impression as a defender was far from convincing, but it was the complete package that made Barcelona spend their euros.
He had the versatility to fill in numerous roles. As a squad member, he is more than useful. As a talented individual, however, he is wasted. Busquets is not going to be leaving anytime soon, whilst the need to play him in another position isn't very frequent.
Now is the time for Song to move on to find regular first-team football, as he is more than capable of establishing himself at another top side.
His combative style means a move back to England, where there will be shortage of suitors, would be his best bet.