What kind of weed is this and how should I kill it in St. Augustine

Question

I tried to take a closeup and a far away view. It looks a lot like the St Augustine but it's clearly not when looking at the root system.

Thanks in advance!

Edit: I think it might be crab grass. Can this be confirmed? Also looking for best way to control it.

It seems to be growing in a rough patch of the yard where the St. Augustine can't take hold.