Too late, as Tcjim mentionsed, you should make sure you have a good "crown"; don't cut it off with a Bobcat. That is, the field should gradually slope to be about 18 inches higher in the center, so that any excess water drains off evenly to the sideline drain areas. A professional with a laser-guided system can do this properly.
Is this Bermuda grass? If not what species? What kind of seed? Do you have a maintenance plan? You want to avoid this level of degredation in the future. Soil test result? Soil type? Is it irrigated? Does field have drain tiles? Low spots where water collects are best corrected by drain tiles--not by fill-in with more "dirt". Can you reduce excess traffic? Can you move the goals every day according to a plan--to reduce excess wear at goal mouth?
You should not mix fertilizer and sand--and seed. They do not spread the same--different particle sizes and weights.