Arnesen to leave Chelsea at end of season
News of Arnesen's decision not to seek a new contract once his current deal expires next year follows the club's surprise decision to dispense with Ray Wilkins as assistant manager earlier in the month.
No reason was given for the sudden exit of Carlo Ancelotti's right-hand man, which came just as last season's double-winners were experiencing their first wobble of the campaign.
Arnesen, who joined Chelsea as director of youth development and chief scout in 2005, took over the role of sporting director in 2009.
"The past two years I've worked more closely with the first team as sporting director and it has been a joy to work alongside Carlo Ancelotti and this exceptionally talented squad and staff," Arnesen told the club's official website.
Chelsea gave no word on who might replace him. Spanish newspapers have reported that the club are interested in former Barcelona sporting director Txiki Begiristain.