The victory moved Inter one point above perfect Napoli atop the Italian league table, with Napoli to visit Sampdoria on Thursday.
With 18 goals in five matches, Inter has the most productive attack in the league and also the highest number of different scorers (11) — virtually erasing worries about replacing the 24 league goals that Lukaku scored last season.
“We’ve had a great start to the season but I think we can still improve,” said new Inter coach Simone Inzaghi, who was hired when Antonio Conte stepped down days after leading the Nerazzurri to their first Serie A title in 11 years.
“We lost three key players this summer in Lukaku, (Achraf) Hakimi and (Christian) Eriksen but we’re coming together,” Inzaghi added.
Inter’s third goal came after Fiorentina forward Nicolás González was shown two yellow cards in succession for protests.
ATALANTA GAINING RHYTHM
Considering its high-powered attack of the last few seasons, Atalanta is still working its way into form.
The Bergamo squad beat visiting Sassuolo 2-1 with first-half goals from Robin Gosens and Davide Zappacosta.