Former Black Cats boss Paolo Di Canio bought his 28-year-old compatriot from Juventus for a reported fee of around £6.8 million in the close-season.
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"I wanted to come to England to play regularly. At Juventus, I wasn't given a consistent place in the team," he told the Sunderland Echo.
"And next summer is the World Cup, so I needed to play regularly.
"The World Cup was a big reason behind me coming here."
Sunderland will look to pick up their first Premier League win of the season when they travel to Swansea City in Poyet's first game in charge on Saturday.