It's two mediocre teams, but we've seen "bad Jeff" against both of them before.
I do think spacing and opportunity are a big part of it. I remember a game when Rondo was out, Pierce and KG force fed the ball to Green who initiated the offense. The offense was run through Green and he was given picks, he got some easy layups and his confidence was up and started hitting jumpers as well.
With Rondo he does nothing but sit in the corner and wait for pass for a 3 point shot.
When Green isn't regulated to standing in a spot as a shooter, and he gets some opportunities, he is able to play much more aggressively and surprise surprise, he looks a lot better.
That being said, spacing is also definitely a factor. Last night he had a monster dunk because there was no one in the paint as KG and Pierce spread out their front court so he got an opportunity for an easy dunk.
I expect Doc to try to take advantage of KG/Pierce/Green more and more.