Know Your Role
Crowder, Jimmy, and Iggy are in a very similar boat here. They are all traditionally excellent defenders at all levels of the floor.
Not only are they good defenders though, but they are also all of a certain physical ilk. When dealing with a player who is of the certain playstyle that Doncic is, which is a finesse style, then the thinking is to beat them up or be physical with them because that is how to get them off of their game. You probably hear this a lot when people talk about how to potentially slow Stephen Curry, in example.
If the player is more worried about the contact, physicality, or retaliating with their own physicality, it generally takes them out of the game by getting them out of rhythm, preventing them from doing the things they typically do to achieve success, or throws them off their wits which causes them to lose focus. This is how and where these three will play the biggest parts in defending Doncic when they get their chances.
Derrick Jones Jr. offers a different dynamic. Airplane Mode is very long, gangly, and as we know, athletic. His length and athleticism should not only serve to bother the shorter limbed and extremely less athletic Doncic, but it should also help to magnify his limitations while giving the rest of the team and coaching staff insight as far as how to attack him.
While they won’t be able to mimic DJJ’s athleticism, as athleticism such as his allows you to do things that humans and human bodies shouldn’t do, it should provide revelation. Other players could perhaps cheat or get head starts to get to areas or in positions that DJJ can get to naturally, which could allow others to have a similar neutralizing effect if that were the case. That is how it would happen and how Jones Jr.’s defensive minutes would serve to help the overall goal, outside of simply being a viable defender in those moments.