Viergever was called up to replace Sanchez for defeat to Heracles on Saturday.
Spurs will have a delegation in Amsterdam today, in an attempt to settle on a fee for Colombia international.
And Viergever stated to De Telegraaf: "Until the end of the transfer market, players can leave.
"The amount of €40 million mentioned is not a surprise to me. I think it's getting worse nowadays, and now they have enough money just to make it fun."
He added: "I have no idea if he's (Sanchez) gone, but I think he's busy with a transfer."
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