Back-to-back wins over Chievo and Hellas Verona have moved Milan to fourth in the top flight ahead of their clash with Vincenzo Montella's side at San Siro.
Inzaghi has tasted defeat just once in the league since taking over - a 1-0 reversal against champions Juventus - helping Milan build a five-point lead over Sunday's opponents.
The former Milan striker believes Montella's side pose direct competition for the final UEFA Champions League spot and urged his players to avoid complacency against their rivals.
"We had our best performance of the season against Verona and cannot afford to take a step backwards," he explained.
"The fact we are five points clear of Fiorentina at this stage is already important, as they are direct rivals for our targets.
"If they don't win on Sunday the hunt for third place could get very complicated for them.
"I know the football world well and the dangers that lie in there. We must keep our feet on the ground and every day I tell my players we can't relax, even when 3-0 up.
"We are a team who need to find our confidence and positive results help, but I must also protect the squad from too much praise."