One of the biggest risks when you decide to switch defending ball screens, is the immediate offensive rebound opportunity for a big man against a smaller player.
When facing this kind of defense, realizing about the advantage for his teammate after an hypothetical missed shot, the ball handler can be even more aggressive to try to finish. He can miss the shot but they will have that advantage in the offensive rebound.
Some players have that "instinct" and follow the action to get the offensive rebound (although in my opinion this is something you can practice from the very beginning of a player's career. But how many youth team's coaches practice offensive rebounding skills?)
So with that idea in mind, and trying to reduce the risk of an offensive rebound that will create a high percentage scoring opportunity, a key for the ball screen "switch" defense should be to box out properly in that mismatch situation.
And this is what I want to show you today, take a look at the video and notice how Nizhny's player Evgeny Baburin, right after switching in the ball screen, turns around and looks for the contact against the big man, boxing him out and making it easier for his teammate to get the rebound after stopping the penetration.