London - Assistant coach Ray Wilkins has left Chelsea after the club decided not to renew his contract.
Chelsea chief executive Ron Gourlay thanked Wilkins for his service in a short statement on the club's website on Thursday.
"On behalf of everyone at the club I would like to thank Ray for everything he has done for Chelsea Football Club. We all wish him well for the future," Gourlay said.
No reason was given for the unexpected decision.
Wilkins, a former Chelsea apprentice, had two spells as Chelsea's assistant coach, aiding Gianluca Vialli in 1999 and 2000 before rejoining in September 2008 under Luiz Felipe Scolari. After Scolari left, he linked up with subsequent managers Guus Hiddink and the present incumbent Carlo Ancelotti.
In Ancelotti's autobiography, which was published two months ago, the Chelsea manager said Wilkins was a key part of the London club's recent success.
"Ray is one of those select few, always present, noble in spirit, a real blue-blood, Chelsea flows in his veins. His heart beats in two languages, and that helped me," Ancelotti wrote. "Without him, we couldn't have won a thing, and in particular we would not have started the year at supersonic speed."
Chelsea won the FA Cup in 2009 with Wilkins as assistant coach and claimed the Premier League and FA Cup double last season.
Wilkins was on the bench for Chelsea's 1-0 home win against Fulham on Wednesday.
The former England international midfielder made his Chelsea debut as a 17-year-old in 1973 and went on to play for Manchester United and Queen's Park Rangers, as well as Italy's AC Milan and Scottish club Glasgow Rangers.
Wilkins speaks some Italian from his time with Milan, a fact that Ancelotti has acknowledged helped him to settle at Chelsea.