Alex Song completes his move from Arsenal to Barcelona, signing a five-year deal at the Nou Camp— BBC Sport (@BBCSport) August 20, 2012
Arsenal had announced that Song would be leaving in the wake of their 0-0 draw against Sunderland to open the 2012/13 season, so this was something of a foregone conclusion. Regardless, Barcelona now have a player who can serve as a backup in both the midfield and the defensive line, essentially replicating the role Javier Mascherano used to play before he was converted into a full-time centre back.
The Gunners, meanwhile, probably need to buy a new defensive midfielder, because their best options there right now are Francis Coquellin and Abou Diaby. Rumour has it that they're in the chase for French international Yann M'Vila, and they could simply spend the money (reportedly £16M) that Barcelona gave them for Song on the 22-year-old.