The two sides are separated by a single point after Milan's defeat to Juventus last weekend, but Allegri says he is not scared of the Viola and is focused on picking up three points against Catania tomorrow to keep his side in front.
"We had match point against them when we led 2-0 (in the 2-2 draw with Fiorentina on April 7), but we have a fixture list which allows us, on paper, to pick up points so they don't scare us," he said.
"After a difficult season, we now want to get as many points as possible to seal third spot, which is a fundamental objective to play in the Champions League next season.
"This will give us all the motivation we need tomorrow. We will have more motivation than Catania, but we have also got to be careful because they play good football and won't gift us anything.
"But we will be ready tomorrow. We would stay ahead of Fiorentina with a win, and there would be one game fewer to play."
Although last weekend's derby defeat effectively put paid to Catania's slim hopes of qualifying for Europe next season, their coach Rolando Maran insists their motivation levels are still as high as ever.
Catania have never beaten Milan before, while they have lost all of their games at the top sides, Juventus, Napoli, Fiorentina, Lazio and Inter Milan.
"My thoughts are that this is our last chance to beat one of the big three clubs this season," Maran said.
"That is what our president wants and he is really keen on it. There is a taboo to be broken and we are still looking to reach 50 points."
Allegri has Mario Balotelli back after suspension and the coach expects him to "give us a hand, like he did before his suspension".