I know I'm coming in late to this particular party but the idea that Boat should have gone under the screen when guarding a guy who is shooting 53% from 3 is a little bit silly. Yes, they gave up 2, but if Boat goes under they probably give up 3, and we're going to overtime or a loss.
The screen was set on the baseline - it wasn't a matter of "going under". The two options were to trail him the whole way, or go over the top and jump the passing lane. Trailing is a perfectly fine strategy (going over the top leaves you vulnerable to a back cut), but if you are over-aggressive at denying the pass out to the wing, you can get beat on a curl screen when the player doubles back into the paint. Boat was playing his balls off, so no faulting his effort, but they used his aggressiveness against him - he was trying to stay right in the guy's shirt, but got caught trailing him all the way to the rim for a layup. Of course, if we had a big in the game, we might have been able to cover for him with someone protecting the rim, but DD and Giffey both offered no help.
In hindsight, with no shot blockers on the floor, Boat should have been more careful to deny that cut and been willing to trail the shooter a little more conservatively (and then jump him on the catch if he caught it on the perimeter). But that's completely hindsight with the advantage of studying the film. To me, Giffey's error is more egregious because it is a simple fundamental mistake, and the second time one of our seniors made a dreadful defensive mistake on an important possession (the other was Bazz leaving his man to chase the ball on BC's fullcourt end-of-game play, when Boat ended up with the block - had BC thrown the ball the other way, Bazz's man was wide, wide open).