After passing up a few first-half chances of the first leg of the Champions League last-16 tie, left-back Nicolas Tagliafico appeared to give Ajax the lead when he headed past Thibaut Courtois towards the end of the first half. The home side's celebrations were cut short when referee Damir Skomina stopped to review the footage and ruled that Dusan Tadic had interfered with play from an offside position as he jumped towards the Madrid goalkeeper.
Karim Benzema fired in the game's real opening goal on the hour mark after being teed up by Vinicius Junior. The Amsterdam side pulled level 15 minutes later through Hakim Ziyech, only for Marco Asensio to ensure Santiago Solari's men take the advantage into the second leg in Madrid.
De Jong believes Ajax showed enough to suggest they can find a way back into the game when they visit the Santiago Bernabeu, but it was a "pity" to see the goal taken away.
"As a team we did well. It's a shame that our goal was disallowed. Maybe something like that falls easily in favour of the big club, we've also had that. But we continued well and also had our chances afterwards. Pity that it didn't yield a better result."
De Jong, who will join Barcelona in the summer, got his first experience of a match against his future domestic rivals and one player in particular impressed him.
"It was certainly nice to play against Luka Modric," he told Ziggo Sport. "That motivates extra of course. He is a natural talent and it is really difficult to put him under pressure."
Madrid host Ajax for the return leg of the second round tie on March 5.