Both clubs have again endured disappointing seasons in Serie A. Milan are ninth in the table with eight games remaining, with Inter a point behind in 10th.
UEFA Europa League qualification seems to be out of reach for the duo, leaving them with little more than pride to play for.
But Mancini said: "The derby is an important game, even if it's a little 'poor' compared to previous years.
"As far as we're concerned, it must be the foundation for a relaunch.
"Who has more to lose? Inter are the 'home' team, so arguably it would be worse for us to lose, but in truth the situations are very similar.
"I had hoped Inter would be higher up the table by now and still in the running for silverware. At times our campaign has been negative."
Mancini will have to cope without the suspended Fredy Guarin and Marcelo Brozovic, while Dodo, Hugo Campagnaro and Jonathan are all unavailable.
"It's a shame I can't use the same XI that beat Verona," Mancini added. "But those who play will do well and we hope to continue along that path."
Alexia Putellas: "We’re already the only club to have won the men’s and women’s Champions League, so the only thing even more historic to do than that would be to win it in the same season"
‘Trent has won everything he can for Liverpool, but of those who’ve left that we wanted to stay, who’s actually done better? I can only come up with one’: Reds legend highlights potential danger of Alexander-Arnold moving to Real Madrid
