'We've lost £200m of talent'
Wolves appointed Gary O'Neil in August last year, replacing current West Ham boss Lopetegui, and he ensured they finished comfortably clear of relegation in his first season.
In the summer, Wolves sold defender Max Kilman to West Ham for £40m and forward Pedro Neto to Chelsea in a £54m deal.
O'Neil identified player departures making his job more difficult.
"The club has been through an incredible transition since I came in," he added.
"We've signed some players who will be really good for this club for the future, but we have lost an awful lot. It makes it harder.
"[Since I've been here] we have lost £200m worth of talent. We understand it will be tough. We will knuckle down and get going again.
"Whenever this journey ends with Wolves I'll be proud of it."