Jeff Green isn't dumb. He knows if the C's don't win a championship this season, all fingers will be pointing at the trade.
So he has something to prove. It doesn't hurt he has a new contract coming, either (ask TA).
And we need Jeff to be that X-factor. We need a scoring punch off the bench. That's what we lacked that last season. Hopefully this year we have Delonte/Wafer/Green/Baby/JO(Shaq starting), which has a lot of scoring punch and should be very good defensively as well.
With the inconsistency of the starters (specifically Rondo, Ray and *insert starting C here*) combined with other great starting units in the playoffs, the C's bench will need to be better than the opposition's. If they can extend leads and close gaps, this team will be extremely tough to beat.