He's also a good defender who has the pace to play a high-line, and won't complain if he only gets 20-30 starts a season. When you have a defender who's pretty good at everything but nothing special on the ball, that's pretty much perfect for the #3 defender. I'd be surprised if LVG doesn't think he can improve Smalling.
Looking at age and natural talent and their athleticism, I'd say that Smalling, Rafael, Shaw, Jones, Januzaj, Herrera, Kagawa and Welbeck would be the players LVG is most likely to see as being able to improve and hit a higher level of performances than they've shown in their career so far.