Ball screen actions, probably the most frequently used tactical tool in modern basketball, is extensively studied on both sides of the court. It will be one of the keys during the Final Four, as the teams that will be in Madrid excel in the use of this "art" and have terrific players to execute it.
It would be too long to analyze every single option we will find during the Final Four in one post, so this is a small study about one of them, which I think will be important in the semifinal between Fenerbahce and Real Madrid: Nemanja Bjelica on ball side corner and two smalls on the opposite side. This is often played by the Turkish team, and it will be interesting to see how it will work, and Real's defensive answers.
There are different ways to approach a specific situation from the defensive side. For example, you can have a rule you follow no matter what (e.g. "whenever they play a side screen, we "trap") and you can also consider who are the players involved and then adapt the defense.
Let's take a look at different scenarios (and let's consider the "1", "2", and "3" positions interchangeable. So I won't talk about "positions" but about characteristics of the players at each one). Always understanding that (in the opinion of many experts) the Euroleague's best "stretch 4", Nemanja Bjelica, is in the ball side corner (he is "4")
For opposing teams, it would be wise to avoid 4's defender helps against 5's roll (giving room for Bjelica to receive a quick pass): it is an extremely dangerous situation, Bjelica being a huge threat. He can catch and shoot, and he can drive to beat the defender's close out.
If the defense manages to avoid these two situations, they often play a "5 x 4" ball screen which creates a new advantage either for Bjelica to score, or for their "5" to roll hard when he has an advantage or crush the board when Bjelica drives.
Allow "1" to shoot, go under the screen: if you rather prefer that shot (e.g. when the ball handler is not a great shooter) than any other option the offense can find. As usual, scouting and "numbers" will help in the decision making process. No helps needed, no "Bjelica's threat"
Do not allow "1" to shoot, go over the screen and collapse the paint avoiding penetration: this option should be considered when you think "2" and "3" threats are smaller than "1's". The screener's defender will try to stop the penetration. As helps will be coming from "weak" side (which we could consider "strong" side once the ball handler drives to the middle) those are dangerous shooting opportunities. And the player getting that pass may try to drive against the close out, so the defenders need to be ready to rotate.
Switch and defend the mismatch, or multiple switching: here, one more time, the defense avoids helping from Bjelica. One problem, Fenerbahce players are very patient to find the way to exploit the advantage. It can be inside, outside, or they can keep playing with very good spacing which usually leads to a good scoring opportunity. Having great "one on one" players makes them really dangerous in mismatch situations.
"Ice", deny the screen: so you don't let the ball handler go to the middle and you create a "traffic" situation on ball side. Fenerbahce can be either very aggressive or very patient against this defensive option. The "aggressive" option: as soon as the screener sees it, he cuts hard to the rim, while the ball handler drives baseline and attracts the screener's defender. Then he can find 5 or the wide open man on the side if there are long helps (a good way to avoid a quick roll is to bump from "2's" defender) Obviously you don't want to help from Bjelica, he is ready to hit the corner three! The "patient" option: the screener will pop and they will attack on the opposite side.
Flash / Trap against the ball handler: trying to stop the ball, being very aggressive to stop penetrations, force turnovers… Although Fenerbahce's spacing plus their high quality players helps them find a good option. First things first, you need to take care of the roll man. We already saw what happens when you help from Bjelica. So you're gonna have to work on defensive fakes and get back real quick after the flash.
A lot to study, many decisions to make, and a small post to show the kind of work coaching staffs are doing "behind the cameras"