The Croatia defender arrived in the summer from Lyon.
Fonte told the Daily Echo: "He's a great player first of all, and when you have a great player next to you it's easier to play," said the Portuguese centre-half, whose partnership with Lovren should be given its sternest test of the season so far when Saints visit league leaders Liverpool on Saturday.
"I feel confident with him, we understand each other well. It's always going to get better, because we're still getting to know each other, but from the first moment I had a good understanding with him.
"I know more or less what he's going to do in each situation, and he knows what I'm going to do, so at the moment we're in a very good place and I hope this partnership keeps developing and improving."
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