The Italy international arrived at St Mary's for a fee that could reach B£14.6million, having been lured to the south coast by his former manager at Espanyol, Mauricio Pochettino.
While Osvaldo has struggled in his first three appearances for Saints, Fonte believes it is a matter of time before he breaks his duck.
"You can see in the game his quality, his movement," the Portuguese 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 per cent confident the goals will come."