The pair are far from being best of friends given their recent past, differing styles and their clubs' Serie A rivalry.
Ranieri built up a decent Chelsea side only to be sacked in 2004 and watch Mourinho take over and lead the London club to two Premier League titles.
The debate about how much credit each man deserved for Chelsea's success rumbles on and almost as soon as Mourinho arrived at champions Inter in June, a personal feud began.
The charasmatic and direct Mourinho constrasts markedly with the avuncular and calm Ranieri. The Portuguese has criticised Ranieri's knowledge of English and accused the 57-year-old of being too long in the tooth among other jibes.
Ranieri has mixed views about his rival.
"I don't like it how he creates controversies," he told Gazzetta dello Sport. "I like the fact all players say good things about him -- it shows he has a good relationship."
The long rivalry between the clubs, who have consistently battled against each other for the Italian title, is just as intense and if not more so than the Milan city derby. Inter versus Turin-based Juventus is called the "Derby of Italy".
"The rivalry with Juventus is older, more traditional and linked to scudettos. Instead the rivalry with AC Milan is because we are from the same city," Inter president Massimo Moratti told reporters.
Anomisity between the clubs worsened in 2006 when Juve were stripped of the title and demoted in a match-fixing scandal, leaving Inter to be awarded the championship in a court room.
If that did not anger Juve fans enough, Inter signed Zlatan Ibrahimovic and Patrick Vieira from the then-Serie B club.
Saturday's match at the San Siro is given extra spice because third-placed Juve, on the back of seven straight wins in all competitions, can move level with the leaders with a win.
Injured midfielder Christian Poulsen is doubtful for the visitors while Inter have centre back Ivan Cordoba suspended. Ibrahimovic was rested for Sweden's friendly in Netherlands on Wednesday to leave him fresh for the big encounter.
The cities of Milan and Turin clash twice over the weekend with AC Milan, a point behind Inter in second, visiting Torino in Sunday's late game.
Lazio, beaten 1-0 by struggling AS Roma in last weekend's Rome derby, look to recover at home to attack-minded Genoa in Sunday's main programme of matches.
