The troublesome assist: How significant is Bird's league-leading assist average?

Seattle Storm point guard Sue Bird is leading the WNBA in assists, but that number alone is not what makes her the best point guard in the WNBA this season. Photo via Kailas Images.

After the Seattle Storm's 82-60 victory over the Los Angeles Sparks last week, it should be no secret that the Storm do well when point guard Sue Bird is aggressive as a scorer.

However, her league-leading 6.7 assists per game through 10 games as a passer are also noteworthy.

In an article yesterday about Storm coach Brian Agler, Kevin Pelton of StormBasketball.com described how Agler has maximized his talent, particularly in the way he trusts players like Bird.

STORM: Agler's Success Adding Up
A major part of that has been the trust Agler has placed in his veteran players, including giving Bird latitude to control the offense on the floor.

"The cool thing about Brian is he trusts me," Bird said. "He lets me run the show when I'm out there. Of course he has his input, just like every head coach, but there are times when if I want to call a play or I think something's going to work, he lets me do that. As a player, to know you have your coach's trust gives you confidence to do that."

Thus far in 2010, Agler's trust is going a long way. Bird is not just leading the WNBA in assists - she's putting up a career best in assists per game. As should be expected by now from Storm players, Bird downplayed it.

"Assists are funny," said Bird. "I don't think that I do that many flashy passes or things like that. I just try to get the ball to the right person at the right time. And then at that point, my teammates are doing a great job of knocking down shots and getting open, using screens, that type of thing. So to me it's kind of a two-way thing...I get the credit for the assists, but it's definitely a lot to do with what my teammates are doing."

Indeed, there is in fact good reason to downplay the value of assists, though they are often used as a proxy for point guard quality it's been pretty well documented that they are misleading, unevenly reported, and of marginal value to teams as a whole. As 2010 NBA assist leader Steve Nash once said in a Wall Street Journal article about NBA assists, "Assists are an indicator of what someone's contributing to their team. They're not a science, though. During the game you don't know if you're getting credit or not, so I don't really care."

Although neither Bird nor Nash put much stock in assists, the fact remains that they do show how much someone is contributing to the team as a distributor. In particular, if it seems that a player is able "to get the ball to the right person at the right time" consistently, then it means there is some skill involved beyond coincidence. When looking a bit more deeply at Bird's overall performance thus far in 2010, the fact that she is accumulating these troublesome assists at a career-best rate is actually quite impressive and makes her pretty convincingly the best point guard in the league so far this season.

When asked for his thoughts on Bird's league-leading assist average, Agler also mentioned the benefit of having a number of teammates to finish but also provided some additional insight.

"I think in general the ball is in her hands quite a bit," said Storm coach Brian Agler. "I think her teammates are recognizing that she's a great playmaker...I think they understand the more Sue has the ball in her hands, the better it is for everybody. So I think that's the understanding."

Without watching every single second of every single game to figure out just how much more often Bird has the ball in her hands this year compared to previous years, we can use Bob Chaiken's metric for touches/minute, which estimates the number of times a player touches the ball in an attacking position on the floor.

Two interesting things emerge when looking at touches for this season. First, although Bird has had the highest percentage of the team's overall touches both this year and last, her percentage of team touches has risen while everyone else's has declined. Second, Bird's touches/minute have risen from 1.44 to 1.63, currently second in the league behind the Tulsa Shock's Natasha Lacy (1.80). So just as coach Agler has put more trust in Bird, it appears like her teammates are actually reflecting that trust in her while on the floor.

However, while a player could conceivably get more assists with more touches without changing the rate at which they get assists, more impressive is that Bird has increased her assist ration quite significantly. John Hollinger's assist ratio is an opportunity rate measuring the percent of touches on which a player gets an assist. Last season, Bird had an assist ratio of 28.82% and ranked 16th in the league. Thus far, this season Bird has an assist ratio of 34.39% and ranks 5th in the league. So she not only has the ball in her hands more often, but is also making assists more often when she has the ball.

Yet as troublesome as assists are, assist rates might be even stranger. It's probably hard to think of 15 point guards in the league one would rather have than Bird and certainly difficult to imagine that Atlanta Dream guards Shalee Lehning and Kelly Miller and New York Liberty guard Leilani Mitchell - three of the four guards ahead of Bird (Sparks guard Ticha Penicheiro leads the league at 57.06%) are better than Bird by any standard. So it helps to contextualize Bird's assist ratio with a few other fun facts.

The most important thing to note is that despite having the ball in her hands more often and looking "to get the ball to the right person at the right time", Bird is averaging a career-low in turnovers as well. In fact, at 1.70, it's the first time she's under 2 turnovers per game in her career. However, again the number of turnovers for a player averaging over 30 minutes a game might be less important than the percentage of turnovers she gets on per 100 plays. This season, Bird is at a career-low at a turnover percentage of 13.3%, second lowest of any point guard in the league.

Of course, the fact that Ashley Houts has the lowest turnover percentage of any point guard in the league at 11.26% should raise an eyebrow as well. However, the big difference between Houts and Bird is the assist rate - Houts is at 23.29%, 28th in the league. In other words, Houts does turn the ball over less, but also touches the ball less - she is neither responsible for the risk of making a play for her teammates nor taking those risks as often.

The element of risk taking involved in creating an assist is exactly what John Hollinger's pure point ratio takes into account - it "fixes" the standard assist to turnover ratio by adjusting for the fact that good point guard both play more minutes thus get more touches and therefore produce more turnovers because they take more risks.

In 2009, Bird had a pure point rating of 3.57, good for 14th in the league. Thus far in 2010, Bird has a pure point rating of 8.53, good for 2nd in the league behind Ticha Penicheiro (9.15) who pretty much owns this metric in women's basketball. These numbers will fall as the season goes on, but for right now Bird is playing remarkably well.

But with Penicheiro keep popping up as ahead of Bird, what separates the two? Obviously, scoring as described previously about the Sparks game.

When Bird is aggressive, the team plays better. However, what makes her particularly special this year is that she's been both aggressive and efficient. Both her scoring average and usage percentage are down this season, which is certainly partially explained by the increased assist ratio. Yet although she is shooting slightly less thus far this season, her efficiency has gone up by almost any standard - not career-high stats, but among the league's distributors she's a reasonably efficient scorer.

One metric that is helpful for point guards is what I have called Chaiken's efficiency ratio, which measures a player's points per empty possession (missed shots, missed free throws, and turnovers). In other words, the combination of pure point rating and Chaiken's efficiency ratio tell you a lot about how much you can trust a point guard. Bird is fourth among distributors in that metric and considering that Phoenix Mercury wing Penny Taylor (who, as an side, is having a phenomenal year as a playmaker) and San Antonio Silver Stars guard Becky Hammon handle the ball less than Bird as a lead guard and Ashley Houts doesn't get near the minutes of the others, one could assert that Bird has the best among "point guards".

Regardless, right now, Bird gets more touches per minute than any starting point guard, gets assists on about a third of those touches, and has become a more efficient scorer than last season. We can have a debate about Bird's defense before anointing her the top point guard in the league, however it's worth noting also that Bird's net plus/minus is also the highest in the league right now meaning that when she is on the floor her team is just better offensively. 17.1 points better in fact. And if she's running the offense so efficiently that she helps her team score, that actually helps the team's defense because it's hard to get transition baskets if you're always taking the ball out from under the basket.

The bottom line is that Sue Bird is having an outstanding year as a point guard and leading the league in assists probably only scratches the surface of understand how good a year she's having. So although one could easily conclude that Bird's assist numbers are inflated because she's playing on a good team, the fact is that she's a very significant part of what makes this franchise best offense a franchise best 9-1.

Related Links:

Bird's aggression, Little's energy lead a balanced Storm attack against Sparks

WNBA preview (Pt 2): What distinguishes "good" point guards from "great" ones?

NBA HD: Dismantling the Assist | Hardwood Paroxysm

NBA Game Charting: the value of a 'Potential Assist' from 82games.com

Count The Basket » Assist Rates

How Valuable is a Helping Hand in Hoops? - The Numbers Guy - WSJ

Assists: The NBA's Most Misleading Statistic - WSJ.com

How Point Guards Influence the Game – Part 2

Swish Appeal statistics glossary

Transition Points:

  • I have used the phrase "assist ratio" and "assist rate" interchangeably in my writing as well as "usage rate" and "usage percentage" in addition to "turnover rate" and "turnover percentage". For the record, the formulas I typically use are "assist ratio" and "usage percentage". For teams, I use "turnover rate" and for players I use "turnover percentage".  All of that is described in the Swish Appeal statistics glossary.
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