Siena twice took the lead at San Siro with a Massimo Maccarone brace and Albin Ekdal, but goals from Wes Sneijder and Water Samuel clinched the points for Inter.
Mourinho said: “We won because we were fortunate, but also had incredible character of a side that never gives in and had immense courage. Even when we got back to 3-3 we could've sat back and protected the point, but not us. We fought on and got all three points.
“I am sorry for Siena, as they didn't deserve this either and it's painful to lose in these circumstances.
“During the match I had a moment where I thought it would be my first home defeat in eight years, against Siena and Malesani. I liked it! I'd prefer to lose to him and Siena to a Coach and team I didn't like.
“For three seconds after the equaliser I thought it was a good point, then I decided no, we had to risk it. In four minutes anything can happen and it certainly did!”
Juventus and Milan were in their hotels watching this game tonight, as they go head-to-head tomorrow evening.
“We knew Milan and Juventus were incredibly happy at the 87th minute, fairly happy at the 88th and at the 93rd maybe some televisions got thrown out the window!
“This match was lost. It was lost. A point would've been probably right considering the football from us and from Siena, but it was a victory of character and luck.”