The Scot joined the Blues as a player in January 1987 and the defender helped the club win the FA Cup, League Cup and European Cup Winners' Cup before retiring in September 1998.
He went on to become to become Ruud Gullit's assistant at Newcastle and had a brief spell as caretaker manager at the Tyneside club after the Dutchman's exit in August 1999 before working under Sir Bobby Robson at St James' Park.
Clarke returned to Chelsea - where Zola enjoyed a successful playing stint between 1996-2003 - and has assisted Mourinho, Avram Grant and current Chelsea boss Luiz Felipe Scolari.
Scolari held talks with Clarke on Wednesday and the Brazilian admitted he would be "sad" to lose him from the coaching set-up.
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