I just stumbled upon the "Real Plus-Minus" stats here:
http://espn.go.com/nba/statistics/rpm/_/sort/DRPM/position/1I thought some of the Celtics fans might find some of the following facts interesting...
1) Marcus Smart ranked 11th among PG's in 'Defensive Real Plus Minus" and 23rd in "Offensive Real Plus Minus". His overall "Real Plus Minus" stat of +2.02 ranks 15th among all NBA Point Guards, putting him above some interesting names:
Darren Collison
Mike Conley
Ty Lawson
Brandon Jennings
Jeremy Lin
Isaiah Thomas
Reggie Jackson
Derek Rose (elbiet injured)
Kemba Walker
Mo Williams
This is a nice indicator that Smart really does impact the team more than his stats would suggest, because there are some pretty nice players on that list.
Surprisingly Smart's ORPM is actually higher than his DRPM, indicating that he actually has even more positive impact on Boston's offense then he does on their defense - didn't expect that!
Avery Bradley is not far behind Smart in terms of defensive impact, but he has a negative offensive impact (-1.02) which puts him at an overall slight negative (-0.44). Both Bradley and Smart rank top 15 among PG's in defensive impact though, which shows why we are so tough to beat when they are out there together.
Isiah Thomas ranks a whopping 12th in the NBA (among ALL players, regardless of position) in ORPM with a +4.16 result. This means that there are only 11 guys in the league who impact their teams offense as much as Thomas does for Boston. Unfortunately this is somewhat negated by the fact that he has a negative (-3.41) defensive impact, but his offense helps the team more than his defense hurts it (+0.75 overall).
Another interesting one - Jae Crowder ranks 16th among Small Forwards in OFFENSIVE RPM (+0.85) but unfortunately is a -1.09 for DRPM. Big surprise as I always felt (from the eye test) that he impacted the game more with his defense.
Boston's top ranked PF was Jared Sullinger, with an ORPM of +1.41 and a DRPM of +0.09 (total of +1.5 is 22nd among Power Forwards).
Amusingly, that wasn't Boston's best at the position. Jonas Jerebko has a +0.91 on offense and a +1.34 on defense. His total RPM of +2.25 is good for 15th among all Power Forwards.
At the center spot, Kelly Olynyk gave me the ultimate shock. His ORPM (+1.74) ranks third among all centers (below only DeAndre Jordan and Marc Gasol :O ) while his defensive RPM of +1.54 was actually good for 29th among centers. His total Real-Plus-Minus of +3.28 is 8th among NBA centers, 42nd among all NBA players, and first among all Celtics.
So in terms of total positive impact on the team, the Celtics leaders are:
1) Kelly Olynyk (+3.28)
2) Jonas Jerebko (+2.25)
3) Marcus Smart (+2.02)
4) Jared Sullinger (+1.5)
5) Isaiah Thomas (+0.75)
6) Tyler Zeller (+0.3)
7) Jae Crowder (-0.24)

Luigi Datome (-0.24)
9) Avery Bradley (-0.44)
10) Gerald Wallace (-1.03)
Yeah, I chuckled at the Gerald Wallace part too - top 10 on the team?? haha I'll put that down to a combination of his hustle and small sample size.