Manchester United scouted Isco several times when he was still at Malaga before his move to Real Madrid.
"He's good, but not quite quick enough and his head is too big for his body," wrote the scout reporting back to Alex Ferguson.
Isco was named man of the match in Real Madrid's 2-1 European Super Cup win over United on Tuesday.
"The midfield players of Real Madrid there are only one, there are no replicas," said Jose Mourinho.
"No replicas of Modric, Toni Kroos, Isco, no replicas of Casemiro, so they are really solid and the way they move the ball makes it difficult."