REVEALED: Why Arsenal sell Alex Song to Barcelona

Arsene Wenger sanctioned the £15million sale of Alex Song to Barcelona after becoming infuriated by the midfielder’s lack of commitment in pre-season.

And it has emerged that the Cameroon midfielder’s exit has been in the offing for months after a breakdown in the relationship between player and club over an improved contract.

Song will complete a switch to the Nou Camp on Monday — sealing the departure of a second key Arsenal player in less than a week. But unlike the £24million sale of Robin van Persie, who was in the final year of his contract, to Manchester United, the Gunners were under no pressure to offload Song, who had three seasons left on his £55,000-per-week deal.

Club sources claim Song’s levels of professionalism had dropped significantly in recent months and Wenger decided enough was enough earlier this summer.

Sources also say Song regularly arrived late for training, took a half-hearted approach in sessions and did not follow instructions from the management staff.

Having established himself as arguably the club’s second-most influential player behind Van Persie, Song felt he was entitled to an improved contract and tried to open talks over a pay rise.

He will earn around £70,000 a week at Barcelona.

It is understood Song’s advisers tried to initiate contact over a new contract in January.

However, sources close to Song insist Arsenal delayed attempts by the 24-year-old to negotiate, leaving the player disillusioned.

Song is said to have been desperate to commit his long-term future to the club, but felt his salary should have been on a par with other top earners.

Ultimately, Arsenal felt offering Song fresh terms was not a priority.