After going through the 2018 FIFA World Cup as an unused substitute, the 23-year-old proved his worth in Luis Enrique's opening two games as manager.
"We have never had a midfielder like this," he said. "Finally people have realised the talent that this man has.
"As an 18-year-old he was offered to Everton and they said no, as a 20-year-old he was offered to Manchester United and they said no but I think in the next couple of years we will be talking about him as one of the top, if not the top midfielder in Europe.
"He can play in the Simeone style without the ball, quick putting teams under pressure, but also in the Barcelona style if he wanted to, quick with his passes.
"And of course, he has got the physique to come from deep as he did with one of the goals against Croatia. You have got everything in one player."