Inter boss Jose Mourinho, who guided the side to an unprecedented Italian treble, wants to coach Real Madrid and is poised to hold talks with the Serie A champions about leaving.
Serbian Mihajlovic, who departed as Inter assistant coach in 2008, made no reference to Inter in his resignation letter but fans will now be wondering about his motives.
"I hope to soon find a job which legitimises my decision and my professional ambitions," he said on Catania's website, apologising several times for the distress he has caused the club.
The former Inter hardman kept modest Catania comfortably in Serie A this term in his first season in charge and the Sicilians beat Mourinho's side along the way.
Mihajlovic, who had an unsuccessful spell as Bologna coach last year, is well known to Inter president Massimo Moratti and only left as assistant because good friend and coach Roberto Mancini was sacked.
Liverpool boss Rafael Benitez has also been mentioned as a possible replacement for Mourinho should the Portuguese complete the formalities of his move to Real.
Mourinho is poised to quit after becoming disillusioned with the cynical world of Italian football despite his stunning success.
