Diers top line speed, at 20-23 was really good.
However, as his body filled out, he may still have high top end speed (like Kulusevski thinks he has). Yet, ask him to turn and run, about half to 3/4 of attackers in the Prem are 10yards clear, before he gets anywhere near “full pelt”.
TBH have similar concerns for VDV in a year or three, very naturally thick set, hope he hates the gym (or bulking anyway).
VDV looks naturally slender to me.
Either way, I hope he builds core strength without bulking up. His comparative advantage is his speed and agility.