Dirt patches in back yard
I would guess that these bare spots with patches of grass might be due to a fungus called “brown patch”.
Here are some sites that will give you further information about this disease;
Sometimes bare spots with tufts of grass are due to excessive amounts of fertilizer that might have been added. I would suggest that you rake these areas to remove any dead grass and water well. If no improvement is seen within a couple of weeks, add some fresh top soil and spread new grass seed. These areas look like that might not be receiving a lot of sun. So in your reseeding avoid blue grass but instead sow perennial rye grass and/or tall fescue. The following site will give you further information of growing grass in shady areas: