Your online friend is entirely too frugal with images!
I would want to not only see tops/bottoms of several leaves (with some kind of scale, though maybe those are 6" deck boards under the latest image), but also a branch with leaves clustered on it, closeups of buds, and maybe an historical image of the tree before it was dismembered (if he's got one).
Does he know if it ever has any appreciable fall color? What sort of soils is it growing on (texture, pH range, moisture levels)? Does he know the general plant communities of the area, and the oak species composition thereof? Sometimes, proxy data can point in a good direction.
With no more information than has been given, you are about as close to an answer as might be expected. Both those species (but also quite a few more in the Red Oak group) will be found in the Nashville region, and they likely can all cross with each other.