This is a Carex, such as C. annectens, triangularis, fissa, etc., etc., etc. Most of the 636 recognized US species are indeterminate by looking at Internet photos, which are often carrying incorrect labels. A "good" ID for Carex usually requires an entire, mature specimen in hand (including the root), a dissecting microscope, a very good dichotomous key and a talented reviewer.

It looks like crabgrass, but When was this photo taken and what part of the south are you in?

You're out of my normal range in terms of recommendations, but... Your lawn actually looks quite good from the middle distance, so that brings up the question as to your goal here. Making some normal assumptions, we'll start with the normal questions. Do you know what you currently have? I can't ID that from the far shot and I'm lousy at grass ID anyway. What is your watering and feeding regimen? Things will differ depending on whether you currently have a northern or southern lawn, although both tend to prefer deep and infrequent watering. A northern lawn down there will need more frequent watering, I'm thinking--perhaps every 5 days in the hottest part of summer, while a southern lawn shouldn't need to be soaked all that often as TN isn't Texas in terms of heat. But in both cases, you'll want to add about an inch of water all at once if the soil will support that (sandier soils may require modification for less, while heavy silts may hold more water and need watering far less often). What I'm saying here is that the look at a distance is so good that a simple fix in care may be enough for you to "rescue" this lawn (which does not look like it needs rescuing, half the people here would love it if you dug that lawn up and shipped it to them). But if you explain what bothers you, maybe reseeding really is the solution and we can suggest something for you.

Looks like a variegated sedge to me, Carex species. Perhaps C. morrowii or oshimensis.