Call me crazy (I'm sure you all will) but I predict he will average somewhere between 20/5/2 and 24/7/3
Last year the only chance we got to really see Jeff's potentially was late in the season when he was moved in to the starting line-up.
During that time he averaged about 20/6/3 playing as the second (maybe even third) offensive option, and with no PG.
To me it really looked like he still felt that it was Pierce and KG's team, and out of respect for them (to show them it was still their team) he seemed to defer to them a lot. He would absolutely dominate for a quarter or two, then he'd step back in the shadows and defer to those guys, almost as if he was afraid to look like a ball hog.
This is why I very strongly believed that trading Pierce out was critical to Jeff's development. Towards the end of the season he seemed to really gain confidence and aggression, but he still had moments where he'd step back so that Pierce could have the spotlight.
To me the telling thing last season wasn't he numbers he averaged as a starter (the 20+ PPG). To me it was the efficiency at which he put up those numbers. When he was locked in and determined to score, opposing teams could not stop him As a starter he was averaging 20 PPG on something like 55% FG and 50% 3PT despite the fact that he had no PG to set him up, and most of those points were off isolations and simply catch-shoot opportunities. If he took 10 more FG attempts per game (which he would have with Pierce and KG not there) his efficiency would have come back down to earth, but he would have likely averaged closer to 25 PPG.
This year with Pierce and KG gone (and Rondo recovering) this will be Jeff's team from the start. Unless Danny brings in a big name free agent (like Josh Smith) everything will go through Green. He will likely get double the touches he got last season, and he no longer needs to hide in the shadow behind his elder teammates.
I think he is going to have an absolute monster year and see a similar type of explosion that we saw from Harden when he moved from OKC to Houston. Despite coming off the bench in OKC Harden always played starters minutes, and he averaged around 16 PPG there as the third option on offense. Once he moved to Houston as a primary scoring option (and with modestly increased minutes) his scoring jumped by about 10 PPG up to 26 PPG. I'm not going to say Jeff will average 26, but I think around 24 is a realistic expectation.
There are a lot of non-believes for sure, but I think his development last season from both a basketball perspective and a mental perspective (he became a LOT more passionate and aggressive as the season went on) combined with his increased role will see him make a massive jump. In only a 20-something game span last season as a started he scored 30+ pints at least 3 times. That tells you instantly that this guy, when in the right mode, can be an elite level scorer in the NBA.
The late return of Rondo will I think only help his case. Initially the entire offense will likely go through Green, and that will leave him no choice but to be aggressive and to step up as a leader. Once Rondo returns we will have two guys who have proven they can be leaders and take over a game, and two potential all-stars.
Honestly as much as everybody talks about Rondo, I think Green is our wildcard this upcoming season. As he goes, so will the Celtics. Bradley will play the same elite defence he always has, Sully will battle for boards, defend the post and clean up mess, Rondo will do a lot of everything...but we already know who those guys are. Jeff Green meeting his potential is what will determine whether this team makes the playoffs or stinks like a rotten egg.