This is a major acquisition for the La Liga powerhouse, as the 24-year-old Song is one of the most reliable defensive midfielders in the world. He had been a fixture at Arsenal since 2008-09, making at least 38 appearances in each of the last four seasons.
He played in a total of 204 matches with the English club, scoring 10 goals and dishing out 24 assists during that time. He has also been a major contributor to Cameroon, proving to be a revelation during the 2008 Africa Cup of Nations and making 30 total appearances with the senior national team.
While Song will occasionally get involved in the attack, he really shines on the defensive end of the pitch.
He's big (6'0", 163 pounds), physical and possesses relentless energy. He often ruins opposing attacks with crunching tackles, and with his good ball control, he will be able to feed the likes of Xavi and Andres Iniesta to ignite the Barcelona offense.
Song's biggest weakness is his tendency to wander defensively. He's prone to getting caught out of position, which occasionally has devastating results when his club is trying to defend the counterattack.
Despite that one poor attribute, Song's pros far outweigh his cons. He's a defensive force in the midfield and a capable passer, and with his height and aerial skills, he can be a threat on set pieces.
He may need a little time to adjust, but once Song is comfortable with his new teammates, he will be a key piece in Barcelona's quest to reclaim the La Liga crown.