The 21-year-old is in his second year at San Siro after joining from Sampdoria and already has seven Serie A goals this term, just two fewer than his total for last season from nine fewer matches.
Despite his good form so far this season, Icardi was left on the bench during Inter's 4-2 defeat at Roma in their previous league outing, coming on for only the final eight minutes.
Mancini confirmed that Icardi will be back in the starting XI for Sunday's visit of Udinese, though, with the former Manchester City coach clearly expecting big things from the young forward.
"Icardi or [Pablo Daniel] Osvaldo? Icardi will start tomorrow [Sunday]," he said.
"I went with Osvaldo against Roma because he was fresher. I have faith in both him and Mauro.
"I think Icardi can develop into a top-class centre forward. I have a lot of confidence in him."
Mancini made his return to the club towards the end of November following the dismissal of Walter Mazzarri and he is upbeat about what he has seen in his first three matches.
"I came here to get Inter winning again and to build a great team," he added. "I think we're on the right path. I'm sure things will start to pick up.
"I'm sure that if we hadn't made those mistakes in Rome we wouldn't have lost the game.
"If we hadn't conceded the third right after pegging them back to 2-2 we would have tried to win the game.
"I hope the fans can be our 12th man on the pitch. When we have them behind us they give us a huge hand."
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