Olmo arrived in August from RB Leipzig.
He said, "The player who surprised me the most, now that you know him better, is Casadó.
"Last year he didn't play as much and I didn't know him and this year he's showing a spectacular level."
In addition, he didn't hesitate to choose Pedri as one of the highest-quality players in the Barça squad.
"It's very easy to play with him. I take the ball and pass it to Pedri," he said.
Olmo came through the La Masia system before leaving for Dinamo Zagreb as a 16 year-old.
On the youth system, he added: "There are players like Lamine (Yamal) or (Pau) Cubarsí who are going through the stages with speed... The Fernández cousins (Toni and Guille) are also training with us, with quality... and they are only 16 years old, be careful."
- Get breaking football news faster with the new Tribal Football app! Download now on iOS and Android to stay ahead of all the latest transfers and football updates. Download now: App Store, Google Play