Cavani scored a hat-trick of headers on Sunday as Napoli beat Juventus 3-0 to go second in Serie A, which saw the Uruguay forward join Udinese's Antonio Di Natale - who had hit a brace in a 4-4 draw at Milan - at the top of the league scoring charts.
And Mihajlovic believes the 23-year-old forward, on loan from Palermo, tops any other aquisition. "First it was Ibrahimovic but now you can say that Cavani is the best signing in this league," he said ahead of his team's meeting with Napoli on Saturday in Naples.
"We're expecting a very difficult match," he said. "Napoli strike fear into their opponents but we have a good sign since our last away win was in Naples. And other than that, we also play well against the big teams.
"We have to contain Cavani with the best possible defensive system, we need to limit him even if Napoli aren't just about him."
Although Fiorentina played in the UEFA Champions League last season, Montolivo admits they have moderate aims for this campaign. "We want to get to 40 points (the theoretical number needed to avoid relegation) as soon as possible and then we'll see," he added.