Alex Caruso is an elite defender but he is also about to be 30 years old but he is also on a great contract. he would be a solid improvement over green in terms of defense but green still has potential to be a better player overall but defensively Caruso would give the mavericks a guard who can potentially lock down a point guard or shooting guard to further improve the defense.
personally I would not trade green for Caruso simply because the mavericks have an abundance of guards and consolidating a guard and a small forward for a top notch big wing would be the better situation but the fact that the bulls may be blowing the roster up soon could have teams looking to take some of their talent.
I defend Green quite a bit but this is such an obvious trade for the Mavs if it was offered. Caruso on this team would be awesome to watch. A first team all defense guy for a win now team like us would be a thing the FO would pounce on.