But Vertonghen, who came through at Ajax before joining Spurs in 2012, has not been surprised by the Eredivisie giants' exploits.
The 32-year-old suggested that part of the development in the Ajax academy sees players instilled with a winning attitude and a confident approach.
"That's what they do," Vertonghen said ahead of facing his former club. "Always, when you're six or seven years old, you start and you're in the best team in the league. Always.
"You have to dominate away from home. A draw is never enough. A win is never enough. You always have to win in a certain way. That's what you're seeing right now.
"Ajax are playing at an unbelievable level. You don't expect teams apart from the big countries to do this. They have shown the way to do it.
"They are always a step ahead of everyone else. I'm happy it pays off.
"They just prepare everyone for the highest level. Then the kids that come on, because they almost are kids when they're 18, 19, and making their debuts at 17 sometimes, they are ready.
"They are hungry. They are ready. They are fearless. They feel the support from the academy and they've got confidence in their qualities."
Tottenham face Ajax in their Champions League semi-final first leg in London on Tuesday before next week's return fixture.