Leonardo is confident Inter Milan can build on Thursday's Serie A win over Napoli and labelled his new side "the best Inter in history."
Inter, who parted with Rafael Benitez before the winter break and handed the reins to ex-Milan star Leonardo, prevailed 3-1 over Napoli.
But Milan stayed five points clear at the top of the standings with a 1-0 victory in their first game of 2011.
Leonardo is nevertheless confident his team can start to climb up in the standings.
"This victory is down to the players," Leonardo said. "We cannot forget that we have defeated the second team in the table.
"The players have shown from the start a lot of sacrifice and in difficult times, the team always responds.
"This team has a heart and this is the best Inter in history.
"Now we have to take it one step at a time."
Inter go into Sunday's match at Catania in seventh place, 13 points behind Milan but have two games in hand.
Milan, meanwhile, host Udinese with Antonio Cassano set to earn a starting place in Massimiliano Allegri's squad.
Cassano came off the bench on Thursday to set up Sidney Strasser for Milan's goal.
Second-place Lazio were held to a goalless draw at Genoa in the last round.
The Biancoceleste will look to return to winning ways when they welcome strugglers Lecce to the Stadio Olimpico.
A Lazio defeat would see fourth-place Roma leapfrog their city rivals in the standings provided Claudio Ranieri's men win at Sampdoria.
Roma won 4-2 over Catania in their first game of 2011 and are two points behind Lazio heading into Sunday's match.
Palermo travel to Verona to face Chievo in buoyant mood after their 3-0 win over Sampdoria in the last round lifted the Sicilians to sixth.
Cesena will be under pressure to win against Genoa knowing that a defeat could see them drop to the relegation zone.
The promoted outfit holds the last safety position and is three points clear of 18th-place Brescia.
Brescia, meanwhile, make the journey to Florence to meet fellow strugglers Fiorentina hoping to avoid their fourth defeat in five games.
Cagliari look to stop the rot when they travel to the Ennio Tardini stadium to meet Parma. Defeats to Cesena and Milan have seen Roberto Donadoni's side drop to 15th place.
Rock-bottom Bari will be looking to build on their midweek triumph against Lecce when they host Bologna.
The Galletti stunned Lecce 1-0 on Thursday to bring their 12-game winless run to an end.
