This is why you can't always trust the plus/minus stat.
Smart's stats:
6 points on 1 for 11 from the field, 0 of 8 behind the arc.
3 assists to 2 turnovers
4 of 6 from the FT line
&
2 steals
Yet he has a +20 for the game?
Or, on the other hand, the problem isn't with the stat, but your assessment about what an effective game is.
The problem is that's can be skewed with low sample sizes. In this case, plus minus is lying like a thief. No sane person can interpret smart's stat line and call it anything less than atrocious.
Unfortunately, you are misinterpreting what plus/minus is all about.
The purpose of Plus/Minus is not to analyse a player's stats. It's purpose is to analyse a player's impact.
The entire purpose purpose of plus/minus is to give credit to the guys who impact winning by doing all the little things that don't show up on stat sheets (hockey passes, setting good screens that lead to baskets, playing outstanding defense, boxing out so your teammate can get a rebound, hustling after loose balls, vocal leadership, savvy veteran plays, etc).
The other purpose is to expose the opposite players - those selfish players who are all about individual stat lines, but who hurt the team when they're on the court because they do a lot of negative things that don't show up on the box score (lazy defense, not going after shooters, not boxing out, setting poor screens, stopping ball movement, poor positioning on offense/defense, not executing plays properly, etc).
For example, some players have generated countless turnovers off savvy veteran tricks like 'puling the chair' when defending in the post. This often leads to the offensive player losing their footing and fall over, which in turn usually leads to them travelling, losing the ball out of bounds, or a loose ball that one of your teammates ends up collecting. This not only ends your opponent's possession (and hence, stops them from scoring) but also generates an extra offensive possession (and hence opportunity to score) for your team. That's a potential 4 point swing on a single play, yet it doesn't show up on a stat sheet.
Another example is if you are playing against a great scorer, and you work extremely hard defensively off the ball, so they have to work twice as hard to catch the ball...and when they do it's in a spot where they aren't comfortable. This often leads to any of three possibilities:
(a) The player doesn't touch the ball
(b) The player catches the ball, doesn't see a good opportunity, passes back out
(c) The player catches the ball in a bad spot, can't do what he wants, forces a bad play
Either of the above is a great outcome, and if you are doing this EVERY time down the court, the potential impact that could have on the opposing teams offense is huge - that type of performance could well be the single most important factor in your team winning the game. But if said player has 2 points on 1-6 shooting, 0 assists, 0 rebounds and 1 turnover, then a simply glance at the stat sheet would tell you that the said player had a disgraceful game and did nothing to help the team win.
As with the above examples, if you watch this game it's easy to see some of the areas in which Smart impacted the game in a positive way. His hustle, his ball movement (passes that didn't lead to assists), his defense, his leadership (etc) were all outstanding.
People get too caught up in basic box score numbers, as if a player's individual stats are what determines whether a team wins or loses.
No.
A team's stats are what determines whether the team wins or loses.
Boston was outscoring the Heat by 20 Points Per 100 Possessions more when Smart was on the court, compared to when he was off the court, despite the fact that he had a bad shooting night and generally put up unimpressive box score numbers. That tells you all you need to know about his impact on the game (which was overwhelmingly positive).
Fantastic breakdown of plus/minus and thank you for sitting down and taking the time to prove me wrong with fantastic points instead of using a couple of sentences to tell me I know nothing. Truth is I didn't really understand plus or minus because I was to lazy to go and read about it. While I don't sit here and deny the accuracy of plus/minus, from what I have seen is that it can be skewed in winning efforts.
For example,
CJ Fair ended up with a +26 on the game, but anyone actually watching the game would tell you that he had a marginal game at best.
A fair point, I honestly wasn't paying much attention to fair while I was watching the game so can't comment really until I watch the game again.
That said, looking at the box score alone Fair put up impressive numbers. He had 12 points on pretty efficient shooting (3-6 FG, 2-2 3PT), got to the line a few times (4-4 FT) and had 9 rebounds - all in only 18 minutes of play, and without committing a single turnover.
Guys who produce good box score numbers often do also have a big impact on the game while they are on the court. So even though plus/minus isn't designed to analyse stats, guys with good stats often do also have a good plus/minus.
This isn't always the case though, and those situations where it isn't the case are basically the situations in which plus/minus becomes a valuable tool.
The strength of plus/minus is it's ability to identify the scenarios out there in which the player's individual box score numbers may not accurately reflect their overall impact on a game/team.
As with any statistical measure, you still need to read between the lines when looking at Plus/Minus stats. For example a guy who plays 3 minute per game and is +25 isn't going to have as much contribution to your win as a guy who plays 32 minutes and is a +12. The impact a guy has in 3 minutes of play probably doesn't mean the difference between a win and a loss (unless it's a really tight game) but the impact a guy has in 25-30 minutes probably does.
This is why even though I love using stats like Real Plus/Minus to evaluate player value, the amount of weight I put into it depends on that individual player's time on the court.
If a guy leads the NBA with a Real Plus/Minus of +12, but the said player only averages 5 MPG...then I'm not going to go and sign that guy to a max contract, make him a starter, and build my team around him.
However I might, take watch some game tape of the guy, analyse his game, see what things he does on the court to generate such a high RPM value. If I like what I see, then I might try and acquire that guy on the cheap, as somebody who can hopefully who can come in and impact games off the bench.
If a guy leads the NBA with a Real Plus/Minus of +12, and has started in 78 games while averaging 30+ MPG, then I'm very intrigued in this player regardless of what his box score numbers look like. A result that positive in a sample size that large suggests this guy probably does have a legitimately huge impact when he's on the court.
At least that's how I look at it, anyway.
Smart's Plus/Minus in this game alone may not be enough information to tell us that he's a major impact player overall. But the RPM numbers he put up last year while playing something like 27 MPG as a starter on a playoff team, would have me very strongly convinced that that he is.