The Nigeria international was one of Watford’s most important players in the first half of last season but has since struggled for consistency.
Ighalo has netted just once in 11 appearances this term and his lack of form has been a concern for Mazzarri.
However, Bastianelli believes the Italian can get the best out of Ighalo following a difficult period in his career.
Bastianelli said: “I am convinced that Mazzarri is the right coach for him. He went through rough times (because of his father’s death) but he is now determined and motivated. He scored 16 goals last season and he can even do better.
“I would like to see him partner Okaka too sometimes, Watford really do have great strikers since they also have Deeney and Isaac Success.”