Stats Don't Lie

Whoever’s seen the movie Moneyball can tell you the importance statistics have in Major League Baseball. In the modern era, this importance carries over to the NBA as well.

I was recently reading over a piece published several years ago on the SBNation affiliate Golden State of Mind about advanced NBA statistics. Anyone who has a basic understanding of these stats knows that Offensive Rating (ORtg) and Defensive Rating (DRtg), as well as the combined metric Net Rating (NRtg), are three of the most important measures used when evaluating a team.

Many people have heard these terms thrown around before but may not quite understand exactly what they are or what they are used for. Skip the following section if you already have a solid understanding of what they show.

To start out, it is helpful to note that

ORtg = 100(Points Scored) / Possessions

DRtg = 100(Points Allowed) / Possessions

NRtg = ORtg - DRtg

ORtg shows points scored per game adjusted for pace of play and DRtg shows points allowed per game adjusted for pace of play while NRtg combines the two to give an overall measure. Obviously a team wants to see its ORtg go up and its DRtg go down. These measures are adjusted for pace of play so that the Jazz (one of the slowest team is in the league last season) can be more accurately compared against a team that plays at a higher pace. Take, for example, the fact that the Jazz averaged 100.4 points per game last season (which ranked 28th overall among teams) compared to the Brooklyn Nets who averaged 105.8 points per game, good for 11th overall. Were the Nets a better offensive team than the Jazz? Any reasonable NBA fan knows this is NOT the case. While the Jazz had an ORtg of 110.46 (5th overall), the Nets clocked in at 104.61 (29th overall). The Nets simply played faster which lead to more points, something not apparent just looking at per-game stats. These same principles hold true for DRtg. NRtg subtracts the Defensive Rating from the Offensive Rating to give an overall measure of point differential adjusted for pace of play.

So getting back to that Golden State of Mind article, it turns out that Net Rating is a huge predictor of total wins. An Expected Win formula is given as follows

Expected Wins = 2.54(NRtg) + 41

Last season the Jazz had an ORtg of 110.46 and a DRtg of 106.19. 110.46 – 106.19 gives us a Net Rating of 4.27. If you plug this in to the Expected Win formula above you get

Expected Jazz wins in 2016-2017 season = 2.54(4.27) + 41 = 51.8458 wins

51.8458 wins should set off a red flag. The actual win total the Jazz had was 51. This is startlingly accurate.

Using this same approach from the current season we see the following

ORtg (as of November 24th) = 104.25

DRtg (as of November 24th) = 103.84

NRtg (as of November 24th) = 0.41

Expected wins as of November 24th = 2.54(0.41) + 41 = 42.0414 wins

42 wins says a couple of things. For one, the Jazz’s playoff hopes are definitely still alive. Last season the 8th seeded team (Portland Trailblazers) had 41 wins and this season, given the surprising struggles of mid-tier Western Conference teams, 42 wins could definitely be enough for the Jazz to punch their ticket into the playoffs. One thing to keep in mind is that these ratings are going to continue fluctuating throughout the season. Once we play our December "death schedule" we could easily see our Net Rating drop into negative territory, thereby dropping our expected win total below 40. On the other hand, once Rudy Gobert returns, I think it’s safe to say our Defensive Rating will improve. I think the overall takeaway from this is that the Jazz, despite currently supporting a losing record, are still on the cusp of competing for a spot in the playoffs. Until we see a drastic reduction in our Net Rating this will remain the case. Don’t give up quite yet Jazz fans.

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