The Rossoneri have only lost once in Serie A since late September and many feel they have momentum on their side despite still being six points behind their rivals in the table.
Gattuso said: "We are conscious of having to face a great team like Inter, towards which we have great respect.
"The table says that we are six points back with a game in hand even if the rescheduled match away to Fiorentina will be tough.
"But we can't lose the derby: the title race would not be over even with a draw. We would remain six points adrift of them, but with a game in hand and the fight would still be open.
"We have great conviction. We play well and Leonardo has great merits, but the derby is a story in itself. Inter can frighten teams because they go behind all the time, but then manage to complete incredible comebacks: I am thinking about the game with Siena or that at the San Nicola, when they were two goals down against Bari and still came away with a point.
"Inter have a strength and a squad that worries people. There is Sneijder and Milito who give them great quality, but also Mourinho who worries me because he is someone who doesn't sleep out of trying to find solutions to stop us.
"I know that right now he'll be watching many videos to study us and see how to limit us."