Diego Costa had decided to quit Chelsea before his text message blow up with manager Antonio Conte, it has been revealed.

The Daily Express says sources close to the player say he had already decided he wanted to leave.

The pair had a huge bust-up in January after Chelsea turned down a £67m bid from Chinese Super League Club Tianjin Qianjian for Costa, but patched things up in order to concentrate on the club's title challenge. But with Costa's volatile nature, peace was never likely to hold.

Chelsea last night were not disputing Costa's version of events, but the club are unhappy the 28-year-old had gone public with the news.

Costa's agent Jorge Mendes was locked in talks with Serie A giants AC Milan last night over a switch to Italy that could be a short-term move before Atletico Madrid's transfer ban is lifted in January.