An agent will always side with his client. It's his job to do so. And Jorge Mendes is very good at his job. But to dismiss his warnings as pure fluff intended to wage a PR-battle and manage his client's damaged reputation would probably be folly.
"Mourinho does not stop being who he is and he is still the best coach in the world despite leaving Chelsea."
"When Mourinho left Chelsea the first time, he accepted a tremendous challenge and did what no-one in the football world believed he could do and that was to take on Inter and lead them to win the Champions League, Serie A and Coppa Italia, a truly remarkable achievement. Then he went to Real Madrid and inspired an historic achievement of the Spanish league, beating all possible records against a great Barcelona, and also the Copa del Rey."
"Today, Mourinho is still the man who coached the English champions and even so, he does not need someone to defend him because, I repeat, he has an amazing career that undoubtedly speaks for him."
-Jorge Mendes; source: Evening Standard
In managerial terms, at just 52 years old, Mourinho is still very young. Sir Alex Ferguson, to whom he'll always be compared, won all but one of his Premier League titles after turning 52, for example. It's not at all inconceivable that similar success lies ahead for The Twice-sacked One. With whom that will be remains to be seen, though I can think we can all agree that ideally it won't be with another Premier League team.