And, he has already left one club mid-season. He left Celtic to join Leicester in February and he even said this -
'I understand when I left it maybe wasn't the ideal time and there was a lot of hurt.'
'Hopefully in time they can respect my decision that I made. It was for no other reason than the professional challenge.'
'The ideal timing would have been the summer but I was in a position where I needed to make a decision because the situation at Leicester had changed.'
So basically, if he was offered the Chelsea job, he would feel the professional challenge again.