I've watched just the highlights and you know I'm a big T-Rob fan but he did a very poor job defensively.
When there was a pick-and-roll with his man he didn't attack the guard, instead backing-down to the paint allowing him an open look.
This is a simple mistake that should be corrected. Maybe he was thinking about being inside for the possible rebound but that's not the right way to defend, you attack the guard first. If there's a need for another rotation you don't think about it at that moment, if it's needed you do it later. Also the rebound, there's another big and other players that would box-out, you have to trust the guard to stay with your man (the big man setting the pick) at least for the next few seconds and rotate back to him only when it's the right thing to do.