Mourinho led Inter to Serie A, the Champions League and Coppa Italia last season, but they have struggled in the 2010-11 campaign under Rafael Benitez and Leonardo.
Mourinho has said he will remain at Real Madrid next season "unless the press sacks" him, but it appears the upcoming Copa del Rey and Champions League clashes with Barcelona are destined to play a major role in the coach's future after Saturday's 1-1 draw in El Clasico all but ended their hopes of winning the league.
Talk of a return to Inter is now rife in the Italian press, with Gazzetta dello Sport having reported that Mourinho has pre-enrolled his children at the school they studied in during his time in Italy. The school, in Lugano, is less than an hour from Inter's Appiano Gentile training camp.
"Leonardo is doing good work and it wouldn't be fair to condemn him for the recent results," Zanetti said after this weekend's 2-0 defeat to Parma, but he added: "The doors of Inter are always open for Mourinho after the extraordinary things he achieved with this club."
Marcello Lippi, who has managed Juventus and Italy across two separate spells, believes a return to Inter could be a wise decision.
He told RAI: "If Mourinho and Inter still hold one another in high esteem, why not? Making a return isn't always a bad idea.
"When I returned to manage the national side [having won the 2006 World Cup], that didn't work out, but before that I'd gone back to Juventus, and I won two league titles and reached the final of the Champions League."
Mourinho recently praised Inter president Massimo Moratti as "an incredible man who shows the football world what a president should be".