playing big one year. By your criteria, BYU's had one definite BIG win in its history (Miami) and maybe two or three other possible BIG wins (Kansas State - Cotton Bowl, TAMU - Kick-off classic from the Cotton Bowl year, SMU - Miracle Bowl).
Just being further rational and hoping that we don't think "big wins" (by your criteria) were ever frequent occurrences in BYU history but are now somehow conspicuously absent under Bronco.