The former Roma striker is yet to find the net for his new club after three Premier League appearances.
However, Fonte is confident that the Italy international will soon start scoring for Mauricio Pochettino's side.
"You can see in the game his quality, his movement," the Portuguese defender said.
"He's creating, he's lively, he gives us something different. He gives us some speed and some penetration and some good skills.
"He's top class and I'm 100 percent confident the goals will come."
Fonte, who has featured in all his four of his side's Premier League games this season, also revealed that several members of the Southampton team have helped Osvaldo to adapt.
"We've taken care of his house, we've taken care of his car." he added. "He's finding it really easy, because everyone is a good person in this club.
"You adapt very quickly and he's completely settled.
"We embrace (new signings) straight away, because without team spirit and togetherness we're not going to achieve anything."
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