They're a "lock" (silly term to use, Vandenberg could blow his knee out and then they're screwed) because they will probably be, at worst, 4-1 after their first 5 games. At that point they'd have home games remaining against Penn State and Purdue along with road games against Indiana (who will be awful) and Northwestern (who probably won't be very good) still on the schedule. It's not very difficult to find 6 wins on their schedule if you assume they're healthy.