Ok back to the original topic, I believe 2 keys to the game are:
(1) Officiating, particularly in the paint
I think we will see a similar strategy from Butler as New Mexico (and others) employed. Basically try to neutralize our size advantage by being physical and trusting that the refs will not blow the whistle on every possession. In the first half against NM we started to pull away and the refs let them scratch and claw their way back into it. Unfortunately I don't see us having another +30 rebounding advantage, so we will need to hit free throws and a few outside shots if the officiating is tight on the outside and soft in the middle.
(2) Butler's outside shooting
Purdue can overcome mediocre outside shooting and win this one. Butler cannot. The 3 point line is the puncher's chance for anyone big or small to get a couple guys hot and carry a team to victory. It happens to us every year like clockwork against 1 or 2 teams in the nonconference. Last year was Vandy and Gardner Webb. This year I could easily see it being Butler.
We've been lucky so far that almost nobody has "gone off" on a hot shooting streak against us from the perimeter. I think part of it is the defense, but there's been some very good opportunities for teams that they've literally crapped the bed when given.
Butler likely will not be one of those - we will need to have our perimeter defense "on" against them.