Mourinho: Inter would have won with seven men
Inter moved nine points clear of second-placed Milan despite Wesley Sneijder's 27th-minute red card thanks to goals by Diego Milito and Goran Pandev.
Brazil defender Lucio was also sent off in the closing stages for handball, although Inter keeper Julio Cesar saved the ensuing penalty by Ronaldinho.
"We showed everything. The only way we would have lost is if we'd gone down to six," Mourinho told Sky television.
"With seven we'd have won the same.
"Inter played a spectacular match from all points of view, tactical, physical, psychological - an incredible match."
The Portuguese coach was less happy with the officials, especially regarding Sneijder's red card for giving the referee sarcastic applause.
"I go away with a strange taste," he said. "It's your country, your championship, it's your problem, not mine.
"Today everything was done for us not to win this match.
"The referee asked if I'd be angry if one of my players clapped at me ironically. I said no, it's part of the game."
Milan coach Leonardo was not downbeat despite a defeat that landed a massive blow to his side's title ambitions.
"One game cannot establish how good you are," he said.
"We have lots of possibilities. We have a game in hand. We have a good position in the standings. We are in the Champions League.
"We encountered Inter on a great night."