Any process that decreases the rate, frequency, or extent of formin-nucleated actin cable assembly. Formin-nucleated actin cable assembly is the aggregation, arrangement and bonding together of a set of components to form a formin-nucleated actin cable. A formin-nucleated actin cable is an actin filament bundle that consists of short filaments organized into bundles of uniform polarity, and is nucleated by formins.