"It was the time of the 'Galacticos', when these players were more important than developing the young ones," Portugal told Radio Marca.
"When Giovani was 14 years old, we had the chance to sign him. The same with Messi," he added.
"I could have also had Cristiano Ronaldo. It was a shame, but during that era the youth set-up did not have the money for signing players."
Today's Mirror reports that United are still interested on Dos Santos who is at Barcelona.