Spurs travel to St Mary's today.
"They have a strong team, I've seen them a few times and they play 'proper' football," Vertonghen told the Spurs website. "They really want to play and believe in their own philosophy.
"They score a lot of goals, but concede a lot as well.
"We've performed well in our away games, so hopefully it will be the same again on Sunday. We're confident and we hope we can win to stay at the top of the league."