And that's roughly where the Celtics are - a promising student, on the precipice of graduating (to something bigger), taking their schedule too lightly, not realizing the subjects they are enrolled in are harder than expected, and that the folks they chose to work on their group final project aren't pulling their own weight.
Most of us have been there, and in Boston's case, it's not even that these players are being bad teammates, as my metaphor suggests - it's that they aren't being great teammates when it counts most, and at crucial junctures, slip down into just "teammates", who aren't even playing especially well.