Dang, all it took was a 2nd rounder? I would have pounced on that.
But I think it's also the fact that given our cap situation, we'd HAVE to send out a player to facilitate a trade due to salary-matching, even for someone who is cheap. Ainge might want to see a bit of Poirier more going forward to judge what he has, as well as seeing guys like Edwards, Ojeyele, etc. more in spurts. He could still make a small trade for someone like Bertans/Saric/Burks, etc., but I'm guessing he values Ojeyele's defense against guys like Giannis/Lebron, plus he doesn't want to just send Poirier away without seeing him in action a bit more.