Ndamukong Suh, the Detroit Lions’ 6-foot-4, 305-pound defensive lineman, is one of the NFL’s best players. Everyone knows about his ferocity, his footwork and his ability, as New England Patriots quarterback Tom Brady said last week, to “ruin a game” for an opposing offense.

Less known about Suh is his carefully collected network of business titans, a Rolodex that could rival many in the sports world—or the business world, for that matter. He is the NFL’s secret finance nerd.

...