And it's why, as great as Duke's roster looks on paper for next year, I still think UK is potentially better. From all indications, De'Aaron Fox is a beast on D, and Monk clearly has the athleticism and length to be very good on that end (though physical gifts like that aren't everything- Wall and Bledsoe weren't really great on D in college). Even if Duke gets Allen back, a perimeter with Thornton, Jackson, Kennard, Allen, and Matt Jones just does not have a tremendous amount of ability on D.
And Duke is likely going to lose it's entire frontcourt, which is actually not bad defensively. Giles and Tatum are going to be a big step up offensively, but Plumlee, Jefferson, and Ingram are good defenders, and they'll all be gone. UK, OTOH, is adding Bam and Gabriel, both of whom are, at the very least, intimidating shotblockers.