Another factor to consider, and I'm sure his dad will tell him the same: the average NFL career, regardless of where you're drafted, is only a few seasons. It's a brutal game. Injuries all over the place. All kinds of promising guys never get a real shot, because of injuries.
And on top of that, it's a cut throat business. Making a squad is damn hard to do, even when perfectly healthy and with a great college career.
Point is, you probably can't count on much more than the guaranteed money you get from your rookie contract, which is all set in place and dictated by where you're drafted. If you do have a long career and actually get to sign a F.A. deal, that's great, but you can't depend on that.
SO, there could be something to say about weighing the pros/cons/risks of staying with the Gophers one more season and boosting your draft stock vs. leaving early to avoid the risk of injury in college but likely having a lower draft position.