Romelu Lukaku marked his first appearance in an Inter shirt by scoring four times in his new side's emphatic win against Virtus Bergamo.
The Belgium international completed his protracted move from Manchester United on Thursday in a reported €80 million (£74m/$90m) deal, ending weeks of speculation.
He did not feature at all for United during their pre-season campaign, and spent some time training back in his native Belgium with Anderlecht as he sought match fitness.
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The forward wasn't ready for Saturday's friendly trip to Valencia, left out of Antonio Conte's matchday squad entirely for a game which Inter eventually won on penalties after a 1-1 draw.