Cristiano Ronaldo returned from injury and headed Juve into the lead just before half-time but Ajax fully deserved the equaliser scored by David Neres straight from the restart and pushed hard for a winner.
Barcelona-bound De Jong ran the game from the middle of the park and Allegri admitted he was not able to shackle him.
“De Jong is the real source of their game,” Allegri said on uefa.com. “We tried to control him with (Rodrigo) Bentancur in the early stages but, when he understood that, he moved deeper, and the forwards had to work hard on him. He played very well.
“Ajax have great qualities. They keep the ball well even when there are no spaces. I think we defended well even if we had to be better when we won the ball in midfield.
“We suffered after their goal because we were a bit shocked to concede immediately after the break but we defended well and finished the game better.”
Allegri also praised Ronaldo, who had missed the previous four games with a thigh problem picked up on international duty.
— AFC Ajax (English) (@AFCAjax_EN) April 10, 2019
“Once again Ronaldo proved to be on a different level,” said Allegri. “His movements and his sense of timing are simply different from the others.”
Ajax boss Erik Ten Hag was hoping for more but will take confidence from the last round, when his side lost the home leg to Real Madrid only to stun the holders 4-1 at the Bernabeu.
He said: “One-one is not the result you hope for, but it is a result. Last time we lost 2-1 to Madrid at home, so we are still in it. We had some very good opportunities.”
Ten Hag added of Ronaldo’s goal: “In midfield, we were wrong for a moment. Then you see that they can move the game at lightning speed. You can’t afford that.”