Does Defense Really Win Championships in the NBA?

Surely you've heard the phrase during some portion of your life as a sports fan.

Defense wins championships. 

It's an old maxim that gets spoken by virtually everyone involved in the world of basketball—or any sport for that matter. Youth leagues prominently feature coaches who preach the importance of shutting down the opposition. High school locker rooms spit forth the same three-word phrase, as do all practice facilities at virtually every level of the sport.

Even Michael Jordan himself, the greatest player in the NBA's history and one of the foremost experts you can find on the subject of winning titles, has said so on multiple occasions, per Tobias J. Moskowitz and L. Jon Wertheim in Scorecasting. 

The moment had arrived at last. In June 1991, Michael Jordan cemented his reputation as the best player of his era—check that: any era—by leading the Chicago Bulls to the NBA title. As he cradled the trophy for the first time, his explanation for his team's success had a familiar ring to anyone who's ever played team sports. 'Defense,' Jordan explained, 'wins championships.' It might have been the most quoted maxim in the sports lexicon, but because Jordan said it, it now had the ring of gospel. 

Five years later, after his Bulls took down the now defunct Seattle SuperSonics, Jordan explained, "It's been shown that defense wins championships." 

"Defense wins championship, without a doubt," he proclaimed in 1997, following the statement up at the conclusion of his three-peat in 1998 with, "Defense wins championships; that's more evident than ever."

For Jordan's Bulls, it was true. While his teams were more offensively oriented during the regular season, they locked down on the defensive end of the floor when the playoffs began. That became their true identity during the most important portion of the Larry O'Brien Trophy pursuit, the 1993 title-winning team notwithstanding.

But were those Chicago squads aberrations? It's sometimes considered blasphemy to doubt Jordan, but does defense actually win championships?  

Getting to the Playoffs

While advancing past the regular season isn't much of an accomplishment for some teams, it's still a necessity when pursuing a championship. It's literally impossible to win a title without making the playoffs, after all. 

If there's one portion of the season in which defense truly does lead to success, it's during the hunt for one of the postseason seeds in either the Eastern or Western Conference. To show that, it's important that you're familiar with two stats I'll refer to as adjusted offensive rating (ORtng+) and adjusted defensive rating (DRtng+). 

The ultimate goal of an offense is to score as many points as possible, while the primary task for a defense is to prevent the opposition from doing exactly that. Looking at per-game numbers is useful, but it's also a flawed exercise, as pace doesn't factor into the equation. 

The standard forms of offensive and defensive rating show how many points a team scores and allows per 100 possessions, respectively, which allows for a pace-neutral look at the performances of those units. It doesn't allow for artificial boosting of an offense by running at a ridiculously quick tempo, which is how it should be, seeing as those teams also tend to allow more points as well. 

The adjusted part of these metrics standardizes them across eras by comparing them to the league-average offensive and defensive ratings during the year in question, as explained in more detail here. A score over 100 for either stat means the unit is better than the league average that season. The higher the number, the better.

Once those are numbers are calculated for each team throughout NBA history, based upon Basketball-Reference.com's databases and my own, we can look at what I call offensive skew. That shows the difference between a team's ORtng+ and DRtng+ by subtracting the latter from the former such that a positive score indicates a squad was better at offense and a negative score shows the team was superior on defense.

Below, you can see each team from 1950 through the 2013-14 season's offensive skew versus its prorated wins (prorated to 82 games to account for the shorter schedules in the Association's early days):

It just looks like a giant cluster with outliers on both ends. Bill Russell's Boston Celtics, for example, were one of the very best defense-first squads, while Steve Nash's Phoenix Suns truly embodied the offense-first mentality for a successful squad.

But as a whole, defense wins out ever so slightly. Teams with a defensive skew (no matter how large) won, on average, 0.7 more games than their offensive counterparts, and there's a similar disparity when only squads that made the playoffs are isolated:

Again, it's a big cluster, and the same teams stand out as outliers. Once more, defense is slightly favored.

For a bit more clarity, let's look at the relationship between defense and success from a different angle. Rather than analyze how many wins were produced by teams with certain inclinations on the court, we can instead figure out how successful three types of squads were throughout NBA history.

First, we have the ones that failed to make the playoffs, no matter how many wins they earned during the season in which they watched the postseason from home (which may be an anachronistic statement for the teams that played before televisions were commonly found in every household).

The second category is comprised of those who did make it past the regular season, and the final one is solely those that earned a championship. 

So, what are the average offensive skews for those teams? 

With a typical offensive skew of 0.06, teams that did not make the playoffs had a slight leaning toward scoring, while teams that did advance to the postseason had an even stronger slant. But it was one that favored the other side of the court.

Perhaps even more telling is the minus-2.2 offensive skew of championship-winning squads, indicating that they were far superior on the defensive end during the regular season. 

Based on those numbers, defense might get teams to the playoffs and put them in good positions to win championships. However, these numbers are all limited to regular-season performances, not the slowed-down playoffs when everything gets more intense. It's certainly possible for changes to take place between the two parts of the year, as they did for Jordan's Bulls: 

With the exception of the title in 1993, the Bulls of the 1990s improved defensively when games started to matter most, completely changing their identities and finding plenty of success while doing so.

They did become more of an offensive squad during Jordan's final ring-winning campaign, but they were still better at defense than offense from the beginning of the postseason through the 2-guard's epic last shot as a member of the Chicago franchise. 

So do identities typically change once the more important part of the season begins, allowing for stronger defensive leanings than those experienced in the regular season? 

There's no easy answer.

Winning a Title

First, it's very much worth noting that there seems to be a general misconception about the style of play in the playoffs. 

Things do slow down, sure. The pace stagnates as teams value each possession to a greater extent, and while that leads to lower per-game totals, it doesn't mean defenses start taking over. In fact, the opposite is often true, as good offense tends to beat good defense during any one play, and some of the postseason squads are usually the best of the best at scoring the ball. 

Basketball-Reference.com begins providing information about postseason offensive and defensive ratings from 1974, and juxtaposing the numbers for the regular season and playoffs from then through the present provides us with a rather interesting image: 

The postseason numbers come from a much smaller sample, so they can be altered greatly by one or two dominant teams. That's what happened with the sharp dip in 2004, as the point-preventing powerhouses known as the Detroit Pistons and San Antonio Spurs met in the NBA Finals, playing more games than anyone else that year and thus swaying the overall offensive rating. 

But all in all, offenses actually get better during the playoffs.

In 24 of the 41 seasons, the postseason offensive rating is the higher number, as it was this past season. And if the popular truism that defenses take over in the playoffs is actually a misconceived notion based on our eyes lying to us and not factoring in pace of play, does that mean the "defense wins championships" maxim could be false as well? 

Well, that's strange. 

Based on the earlier graph showing that the offensive skew grew more negative for teams that experienced better results, surely this one—showing the results for every team from 1984 through the present day, as the first round expanded to include 16 teams in '84—should show a similar pattern.

But it doesn't.

The biggest aberration comes when teams advance to the NBA Finals but can't get over the hump and adorn their fingers with rings.  

Chalk it up to bad luck, as the 2004-05 Pistons (minus-10.94 offensive skew), 2009-10 Boston Celtics (minus-10.28), 1987-88 Pistons (minus-10.03) and five additional teams with an offensive skew more than five points under zero fall into the category.

Meanwhile, only five squads in the group had offensive skews greater than five, led by the 2011-12 Oklahoma City Thunder (11.45), 1999-00 Indiana Pacers (7.71) and 1988-89 Los Angeles Lakers (5.71). 

Nonetheless, there really isn't a pattern, and it's because having a clear-cut defensive identity really isn't all that important. What's most crucial is just being a better team, as this next graph helps clarify.

It's not as though teams were getting worse at defense as they experienced better results, just that the defensive improvements weren't necessarily outpacing the offensive ones. In fact, there's a more consistent upward trend for the less-glamorous end, which may be the biggest testimony of all for those who steadfastly find themselves in the "defense wins championships" crowd. 

But if you look at every team that's won a title throughout the post-merger portion of NBA history, there's no consistency as to where the primary calling card comes into play. 

In the early days, defense did indeed dominate, but that was primarily because of Russell and those dynastic C's. History has seen the two sides of the ball stabilize, and there have been plenty of teams that won titles with offensive inclinations.

Most actually happen to be quite balanced on both ends of the ball, which plays in with Moskowitz and Wertheim's own research that expands beyond basketball to other major sports: 

But the bottom line is this: Defense is no more important than offense. It's not defense that wins championships. In virtually every sport, you need either a stellar offense or a stellar defense, and having both is even better. Instead of coming with the 'defense wins championships' cliche, a brutally honest coach might more aptly, if less inspirationally, say: 'Defense is less sexy and no more essential than offense. But I urge it, anyway.'

Coaches are still going to urge their players to lock down on the less-glamorous end. Crowds are still going to yell and scream "DE-FENSE" whenever their team needs a big stop. Players are still going to pride themselves on preventing buckets in crucial situations. 

After all, defense does win championships.

The only problem with the popular saying is that offense does too. 

Note: All stats, unless otherwise indicated, come from Basketball-Reference.