That belief was only strengthened by a pair of first half goals, with De Ligt scoring the opener on a thumping header that looked very similar to his finish against Juventus in the quarter-finals.
Hakim Ziyech then provided Ajax's second, giving the Dutch side a 3-0 aggregate lead with just 45 minutes of football remaining.
It all fell apart from there, however, as Lucas Moura scored a pair of goals in quick succession to bring Spurs within touching distance of winning the tie on away goals.
And they did just that, with Moura scoring deep into stoppage time to seal Tottenham's spot in Madrid and Ajax's accompanying elimination.
"When you see the whole game, we didn't deserve to be knocked out," De Ligt told Veronica . "We barely gave anything away in first half, but we're out anyway. Incredible.
"It's a dream getting crushed. I would have loved to play the final, but it's not happening.
"I'm getting goosebumps from the way our fans cheered for us [after the final whistle]. It's hard to say right now, but we have to move on.
"We still have to play two matches to win the title. That's most important now."
De Ligt added that Ajax's inability to pressure Tottenham proved their undoing, as the second half played out much differently than the first 45 which saw the home side cruise without many issues.
"In the second half we were no longer capable of putting on pressure, so Alderweireld could step forward and Trippier had too much time to bring the ball in," the defender said.
"We had no answer to that. We survived for a very long time, but we gave away the goals very clumsily. That's what made the difference.
"The fans gave me chills, but unfortunately it's not our night."
Ajax will now turn focus towards the Eredivisie title as they sit level on points with PSV with two games remaining.