When you play with Lebron and Irving, with a coach who doesn't understand the personal, or players respect, you wont look good. Every ones numbers are down on that team, well maybe not every one, but Lebron and Irvings are at least. He looked good that first quarter against the C's when they ran the offense threw him. Then they went away from that and Boston made their run.
If you get him for Lee, filler and a couple draft picks,(hopefully not all the Nets picks), you do that. He's a systems guy, that would fit Stevens style of play. His outlet passing alone is valuable.