Why not?
We paid £32m two years ago so we'd be doubling our money on an asset that can only deteriorate in value now. If he has made up his mind to move on, we either sell this summer for this sort of price, or we keep an unhappy player and get maybe £30m next summer.
It's all about the new contract. If Tielemans has made it clear that he isn't going to be signing one, we really need to sell him this summer. Our entire business model is based on selling high and reinvesting.
And once again, it isn't just Tielemans. We have both Ricardo and Soyuncu in exactly the same situation with neither player showing any sign of renewing their contracts.