take a closer look.. is it even the same type of grass as the rest???

if not.. just remove it.. and move a few plugs into the empty spot ... and let it fill it ...

ken

That looks like frost damage too me.

How long has it been since the last frost?

First, where are you, what kind of grass is it, and when did that start?

Has a dog been using that spot as a toilet?

My second thought, Tootsie. :-) First being spring, a nice lawn's time for snow mold, minor cold-weather fungi, weird dieback spots, and other oddball things.