Porto have confirmed that coach Luigi Del Neri has left the club before taking charge of a competitive match.
Del Neri is regarded as one of the best young coaches in Italy
Del Neri was named as Jose Mourinho's replacement in June, but apparently angered club president Jorge Pinto da Costa with his poor time-keeping.
Del Neri was late returning from Italy and missed Friday's training session.
A club statement said: "The board of Porto and head coach Luigi Del Neri agreed to interrupt their contractual link for private reasons."
Del Neri built his reputation at Chievo having led the unfashionable Verona-based club from Serie B obscurity to credible Serie A force.