Warnock claims that he was offered van Dijk for six million when the player was still with Celtic, but declined to go ahead with the transfer.
"I went after the centre-half at Celtic, Van Dijk, and they wanted £6million," he said.
"I said, 'We have got to buy him, don't we?' The chief scout went to watch him and said, 'He is not very quick, it's Scottish football'. That was before Southampton came in for him."
Now van Dijk is a 75 million pound defender, after a protracted transfer saga that started during the summer transfer window.