Antonio Conte told Romelu Lukaku he must improve despite the Inter striker's fine form in his first season in Serie A.
Lukaku has scored 23 league goals since signing from Manchester United last year, including four in his past five games.
The Belgium international netted twice in Inter's 3-0 win at Genoa on Saturday, prompting praise from Conte, who marvelled at a brilliant second strike in stoppage time.
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But the Nerazzurri head coach also suggested Lukaku could improve and hammered this message home ahead of Tuesday's clash with Napoli.