Juve left Dortmund with a Champions League point after an amazing 4-4 draw on Tuesday night.
Afterwards, former Juve captain Del Piero told Sky Italia: "We saw a team blocked and covered in the first half and in the second we understood why... There is always a tendency to underestimate the Yellow and Blacks.
"Juve have found a different energy with patience, anger, and determination, right to the end, as is our motto. These things are a positive sign for the team; they are beautiful and very important signs of a vibrant group that trusts each other and the coach. It's a point that is worth more; in all fairness, it's worth three."
Del Piero concluded speaking about Kenan Yildiz: "The goal he scored is amazing, a spectacle of trajectory, I have to congratulate him. The extraordinary thing is the fact that the ball spins as it comes down, with the double effect it becomes unstoppable."