Determine if your mattress is still under warranty. If you do not have a copy of the warranty in your records, view warranty policies at the Sealy website. If it is still under warranty, a sagging problem may still be covered for repairs or replacement. Contact Sealy for more information.
Install a five-leg box spring, especially if you have a queen- or king-sized mattress. A five-leg box spring has a rigid support leg in the center, which helps distribute weight on the bed more evenly.
Use a commercial support product. These are foam pieces cut to fill in a sagging mattress on the underside.
Purchase a piece of plywood cut to the size of your mattress but minus a few inches on all sides from a home improvement store. Pull off the mattress, place the plywood on the box spring, center the wood and then replace for mattress.