Brown patches in lawn
I don't have enough information to make a positive ID. Are these spots in one part of your yard, or all over, sunny or shaded, same size of varied, sandy soil or clay? I suspect dollar spot or brown patch might be your problem. I am attaching links to sites that can help you identify and treat the problem. You may need to look closely at the leaves and/or roots to make the identification. IF you are unsuccessful at identifying the problem, take more clear, detailed photos and email me back.
MSU Turf disease ID
This university is farther away but the info may still be helpful: