Castro, who had previously spent time training with Arsenal and Chelsea, joined the Baggies last month following a successful trial.
The 20-year-old plays in central midfield – an area Albion’s squad currently looks light in.
But after impressing in training, the youngster suffered a blow when he picked up a shoulder injury.
Now, though, he is back in training with Ismael believing he has a lot of the qualities needed to play in his high intensity style.
“He (Castro) came back into training last week,” the boss said.
“Quevin has a lot of quality. He has a lot of principle, aggression for the six position, he’s on the front foot.
“Technically he is very good, he’s a young player who needs to learn a lot but he plays a part in our process.
“He needs to learn, but in that position he’s got great players in front of him to learn from.
“Jake (Livermore), our skip, with Alex Mowatt, he can learn a lot.
“It’s just a question of time with him, when we will see him.
“I want to see him as well in the games, so at some point he’ll have to play to make sure that our feeling with him is the right feeling.”
Ismael admits Castro has surprised him with his quality.
“He’s impressed, he’s very young,” the boss added. “I was really surprised when he told me his age.
“But it’s not about age. It’s about whether you’re able to play like we want, to put the principles on the pitch.
“We want to see that, and if so then it doesn’t matter whether you are 18, 19, 30, 33, you’ll play.
“That was the message from me and my staff from the guys – it was all about the focus on us, on our philosophy and principles.
“We need players who are ready to go with us. Quevin is part of the process.”