Greetings Steve,
Sugar maple, like ash, often has “false heartwood”. False heartwood is usually caused by a wound or opening in the bark of the tree and thereby creates a discoloration of the sapwood.
This "decay" may also be the result of sapstreak disease, caused by the fungus Ceratocystis coerulescens. This disease often causes discoloration of the sapwood. The star pattern you see in the cross section of the wood may be due in part to the parenchyma cells.