Maybe he'll play centrally. His supporters keep telling us he's just as good in a central midfield role.
Doucoure is their best central midfielder. VDB will have to compete with Allen, Andre Gomes, Dele Alli, Gordon, and Gray for some type of midfield role. Probably as an advanced 8 or 10.
Lampard won't have a complete squad for training until next week, and nobody knows how he'll setup Everton. Only way to get Allen, Doucoure, Dele, and VDB on the pitch at the same time is via a diamond central midfield.