Osvaldo is still waiting to score for the first time since signing for Saints from Roma last month, but he was only denied by an excellent Jussi Jaaskelainen save against West Ham United and has shown flashes of his quality.
Centre-back Fonte has been impressed and expects Osvaldo to make a big impact in the Premier League this season.
"You can see in the game his quality, his movement," Fonte told the Southern Daily Echo.
"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."
Fonte says everyone at Southampton has been putting in the effort to ensure Osvaldo adjusts quickly to life at the club, just like they do with all new signings.
He said: "We've taken care of everything. We've taken care of his house, we've taken care of his car. He's finding it really easy, because everyone is a good person in this club.
"You adapt very quickly and he's completely settled. He just wants to move into his house.
"He's still in a hotel, which is not the best, but soon he will move into his house and he will be even more settled."
Fonte added: "We embrace them straight away, because without team spirit and togetherness we're not going to achieve anything.
"We need to get to know our team-mate who comes into the club, make him feel welcome, show him what he wants and what he needs and try and help him so he settles as quick as possible to help us on the pitch."