Sherwood claims he first spotted the winger, 22, when he was an 18-year-old playing for Denmark in a 2-1 defeat by England and tried to convince Spurs chairman Daniel Levy to sign him then.
"I watched him for Denmark in 2011 and I rang Daniel Levy the day after and said that he needed to sign this boy," Sherwood said. "You are always fearful that someone might come and take one of your best players and Christian is certainly one."
But they had to wait three years until they finally secured his services.
"I don't think he was available [at the time]," Sherwood added. "I think he wanted to continue his education at Ajax and that is what happened.
"And perhaps Daniel didn't follow up on it as he does not follow up on every player I tell him, as there are probably too many.
"He had a year left at Ajax. He has been great acquisition for the club and they have done well to bring him in."
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