Inter captain Javier Zanetti feels Rafael Benitez's short spell in charge of the club was hampered by injuries.
The Spanish tactician left Inter by mutual consent in December after winning the Club World Cup and Italian Super Cup.
He had demanded Inter make at least four new signings during the January transfer window, something which offended Massimo Moratti.
Since appointing Leonardo, Inter have gone from strength to strength in Serie A, winning 12 out of 14 games.
Last night's 2-0 victory away to Sampdoria meant Inter moved temporarily into second place, two points behind League leaders Milan.
"We had the same attitude with Benitez," Zanetti said. "But there were 11 or 12 bad injuries, which complicated everything.
"As long as we were at full strength, we did well. Then we lost ground.
"Leo has brought enthusiasm back to us. But we know that everything depends on us.
"If we believes in ourselves we can realise all our objectives, even if it will be tough against Napoli and Milan."
Think you know your Italian football? Share your knowledge, tips and comments to win cash prizes in OLBG's tipster competition - £5,000 monthly.