Friday, January 9, 2015

Best backcourt in the NBA?

There's been much talk about Steph Curry and Klay Thompson representing the best backcourt in the NBA in years (see here, here, here, etc.). I was interested in seeing how the two performed relative to their peers this season as well as the last few seasons to get some broader context of their success.

I pulled data on two-man lineup from NBA stats for the 2011/12, 2012/13, 2013,14 and 2014/15 (as of games played on January 6, 2015) seasons. As there are many combinations of two-man lineups I filtered the population by lineups that averaged playing approximately 20 minutes per game together during each seasons*.  This filter also enabled me to focus on high volume playing time lineups and eliminates the potential for anomalous performance. For each season this resulted in a population of 79 (2011/12), 100 (2012/13), 94 (2013/14), and 145 (2014/15) two player lineups.

Of this population of 418 lineups, I first focused on Net Rating, which subtracts Offensive Rating (points per 100 possessions) from Defensive Rating (points allowed per 100 possessions). The larger the Net Rating the better. The chart below shows the 20 best and 10 worst (for some context) two-man lineups in terms of Net Rating in the NBA over the last four seasons. Klay and Steph's Net Rating of 22.6 is third out of this population of 418 lineups and only trails (and is followed by) two other 2014-15 GSW two-man line-ups. We can interpret this as meaning that this seasons GSW starters dominate their opponents relative to the rest of the NBA over the last few seasons.

The reason for this exceptionally high Net Rating may surprise you. While the "Splash Brothers" are known for the shooting efficacy, they are actually only the 7th best two-man lineup in terms of Offensive Rating over the last four seasons (they trail 6 combinations of the 2014-15 LA Clippers starting lineup). The next chart shows the 20 best and 10 worst two-man lineups but this time just in terms of Defensive Rating over the last four seasons. Unlike Net Rating, with Defensive Rating the lower the number the better.

Again, Klay and Steph are the third best and only surpassed by two other 2014-15 GSW lineups (according to the Defensive Rating metric Kobe and Jeremy Lin combine to produce the worst defense in the NBA in recent memory, i.e., the last four seasons). So not only are Klay and Steph exceptional shooters but they're some of the better defenders in recent history (along with two GSW teammates).

What an aggregate measure, like Defensive Rating, misses are intervening factors (in this case teammates) that may contribute to Klay and Steph's defensive efficacy. In other words, their teammates (Green, Barnes) may be exceptional defenders and Steph and Klay may benefit statistically from the teammates being on the floor. (That being said, Klay can undoubtedly strap and Steph has elected to entertain the notion of there existing a defensive half of the basketball court this season so it is unlikely that their low/ great Defensive Rating is purely explained by omitted factors, like teammates' defensive efficacy).

In light of their defensive success, one cannot ignore Steph and Klay's offensive efficacy. In this last chart I plotted true shooting %, which is a measure that takes into account the value of free throws and three pointers in determining shooting efficacy, and pace, which captures the number of possessions per 48 minutes. These two are relevant measures of offensive efficacy because if a line-up shoots particularly well and they have a high number of possessions relative to the rest of the league then one would anticipate disproportionate offensive output.

In fact, of the 418 two-man lineups in this population, Steph and Klay were 9th in true shooting % (59.9%) and second in pace (102.69 possessions per 48 minutes). The chart below exhibits Steph and Klay's exceptional pace and shooting. In short--the hype is legitimate. Based on high frequency minute two-man line-ups over the last four NBA seasons, it is safe to argue that Steph Curry and Klay Thompson represent the best backcourt in the NBA.

*This amounted to 1,320 minutes in the strike-shortened 2011/12, 1640 minutes in 2012/13-2013/14, and 600 minutes in 201/15, which calculates to 20 minutes per game over 30 games (most teams had played about 34-35 games as of January 6). 

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