Which NBA Teams Have Improved the Most This Year?

Based on win percentage and Net Rating changes, which teams have improved the most -- and taken the biggest step backward?

We're at roughly the three-quarter mark of the 2015-16 NBA season, so we have a pretty good idea of which teams are currently gearing up for the playoffs and which are eyeing draft lottery balls.

Naturally, the teams on opposite sides of the standings are not exactly the same as they were last year. No one season is like any other, of course, and there's perhaps no better way to see that than to compare one year's standings to the previous year's. 

The Chicago Bulls went from the 3 seed in the Eastern Conference and being mentioned in the same breath as the Cleveland Cavaliers as title contenders last year to currently being out of the playoff picture as the East's 10 seed this season. Conversely, the Boston Celtics have gone from barely squeaking into last year's postseason as the 7 seed in the East to being this year's convincing 3 seed. Meanwhile, out West, the Houston Rockets have gone from being last year's 2 seed and a Western Conference finalist to barely hanging onto a playoff spot as this year's 8 seed, only 1.5 games ahead of the Utah Jazz.

Big changes like that are easy to spot, but some teams have had more subtle improvements or taken less obvious steps back than you might realize from last year to now. In order to quantify these improvements and regressions, let's take a look at the differentials in Win-Loss Percentage (W-L%) and Net Rating (points scored minus points allowed per 100 possessions) for every team in the Association from last year to this year, ranking the results by conference.

W-L% Differentials, Eastern Conference

Team 2014-15 W-L% 2015-16 W-L% Differential
New York Knicks 0.207 0.403 +0.196
Orlando Magic 0.305 0.450 +0.145
Charlotte Hornets 0.402 0.533 +0.131
Miami Heat 0.451 0.574 +0.123
Detroit Pistons 0.390 0.508 +0.118
Boston Celtics 0.488 0.597 +0.109
Toronto Raptors 0.598 0.678 +0.080
Cleveland Cavaliers 0.646 0.712 +0.066
Indiana Pacers 0.463 0.525 +0.062
Washington Wizards 0.561 0.500 -0.061
Philadelphia 76ers 0.220 0.131 -0.089
Milwaukee Bucks 0.500 0.410 -0.090
Chicago Bulls 0.610 0.500 -0.110
Brooklyn Nets 0.463 0.279 -0.184
Atlanta Hawks 0.732 0.541 -0.191

The New York Knicks look set to miss the playoffs for the third consecutive year (they are currently 6.5 games back of the 8 seed, and our algorithms give them a 0.0% chance of making it), but they have had the most improved Win-Loss Percentage in the whole NBA from last season to this one. That might be more of a testament to just how bad they were last year at 17-65 than how much better they are this year, but a step in the right direction shouldn't be completely ignored. Kristaps Porzingis isn't about to get any MVP votes, but New York having such a strong building block to team with Carmelo Anthony bodes well for their future. Too bad they don't have their first-round pick this year. Oops.

Other notable risers include the Orlando Magic and the Charlotte Hornets. The Magic flirted with potentially being a playoff team early in the season, but they're just not quite there yet. Still, a +0.145 improvement in winning percentage looks good on such a young team. Meanwhile, the Hornets have gone from being a lottery team to one that could make some noise in the playoffs. They've had the third-best Net Rating in the league since February 1st at 8.5.

As for the fallers, perhaps the Washington Wizards haven't dropped off quite as much as everyone thought they had, maybe their competition just got better. The Philadelphia 76ers somehow keep getting worse, while the Milwaukee Bucks, Chicago Bulls, and Brooklyn Nets have all fallen off considerably after being playoff teams last year. The biggest drop-off in the Eastern Conference and tied for the second-biggest in the league has been the Atlanta Hawks, who went from being a 60-win team and the 1 seed last year to a team on pace for around 45 wins and the bottom half of the playoff bracket.

W-L% Differentials, Western Conference

Team 2014-15 W-L% 2015-16 W-L% Differential
San Antonio Spurs 0.671 0.852 +0.181
Oklahoma City Thunder 0.549 0.677 +0.128
Minnesota Timberwolves 0.195 0.311 +0.116
Golden State Warriors 0.817 0.917 +0.100
Sacramento Kings 0.354 0.417 +0.063
Denver Nuggets 0.366 0.393 +0.027
Utah Jazz 0.463 0.467 +0.004
Los Angeles Clippers 0.683 0.667 -0.016
Los Angeles Lakers 0.256 0.194 -0.062
Memphis Grizzlies 0.671 0.600 -0.071
Dallas Mavericks 0.610 0.532 -0.078
Portland Trail Blazers 0.622 0.532 -0.090
New Orleans Pelicans 0.549 0.383 -0.166
Houston Rockets 0.683 0.492 -0.191
Phoenix Suns 0.476 0.246 -0.230

Somehow, the best team of the last decade and a half has gotten considerably better this year. The San Antonio Spurs are the West's most improved team and people shouldn't sleep on just how good they are just because the Warriors exist. For that matter, our algorithms like San Antonio's title chances (34.9%) better than Golden State's (29.8%).

Oklahoma City's improvement can be chalked up to their having a healthy Kevin Durant, while incremental increases for rebuilding teams like the Minnesota Timberwolves, Sacramento Kings, and Denver Nuggets should have their fanbases nodding their heads in approval. The Utah Jazz haven't made the leap that a lot of people were expecting they would, but their problems have largely been health-related and they're still trending up.

Six of last year's Western Conference playoff teams in the Los Angeles Clippers, Memphis Grizzlies, Dallas Mavericks, Portland Trail Blazers, New Orleans Pelicans, and Houston Rockets have seen their winning percentage fall this season. The drop-off has been particularly harsh for the Pelicans and Rockets. The Blazers' dip was to be expected with all the turnover in personnel this year, but the fact that they're not at the bottom of this list with Phoenix and are actually in a playoff race might make a case for Terry Stotts as Coach of the Year.

Speaking of Phoenix, the Suns have had the biggest decline in Win-Loss Percentage in the whole Association from last year to this season, while dealing with injuries to Eric Bledsoe and Brandon Knight, the firing of Jeff Hornacek, and the whole Markieff Morris fiasco.

Net Rating Differentials, Eastern Conference

Team 2014-2015 Net Rtg 2015-16 Net Rtg Differential
New York Knicks -10.1 -3.0 +7.1
Charlotte Hornets -3.4 2.1 +5.5
Boston Celtics -0.4 4.0 +4.4
Miami Heat -2.4 2.0 +4.4
Orlando Magic -5.6 -1.8 +3.8
Indiana Pacers -0.1 2.1 +2.2
Cleveland Cavaliers 3.7 5.5 +1.8
Detroit Pistons -1.8 0.0 +1.8
Toronto Raptors 3.2 4.3 +1.1
Philadelphia 76ers -9.1 -10.6 -1.5
Atlanta Hawks 5.6 3.1 -2.5
Washington Wizards 1.9 -1.3 -3.2
Brooklyn Nets -3.1 -6.6 -3.5
Chicago Bulls 3.3 -1.5 -4.8
Milwaukee Bucks 1.2 -3.8 -5.0

There's not much to say about these rankings that wasn't said above, but they've been included because sometimes a team's Net Rating says more about its quality of play than simple wins and losses.

The Knicks once again top the list for the Eastern Conference -- and the entire league for that matter -- but once again that's largely because their performance from last season registered a -10.1 Net Rating, which was just plain awful. Other than that, the Bulls' decline in the standings is confirmed by their drop in efficiency, while the Hawks' drop-off in wins and losses doesn't seem so bad here.

Net Rating Differentials, Western Conference

Team 2014-2015 Net Rtg 2015-16 Net Rtg Differential
San Antonio Spurs 6.6 13.6 +7.0
Minnesota Timberwolves -9.8 -3.4 +6.4
Oklahoma City Thunder 1.3 6.8 +5.5
Golden State Warriors 11.4 12.4 +1.0
Sacramento Kings -4.0 -3.1 +0.9
Denver Nuggets -3.9 -3.4 +0.5
Utah Jazz 0.5 0.1 -0.4
Los Angeles Clippers 6.9 6.0 -0.9
Dallas Mavericks 3.5 0.7 -2.8
Los Angeles Lakers -7.2 -10.5 -3.3
Portland Trail Blazers 4.2 0.9 -3.3
Memphis Grizzlies 3.1 -0.3 -3.4
New Orleans Pelicans 0.7 -3.2 -3.9
Houston Rockets 3.7 -1.9 -5.6
Phoenix Suns -0.5 -8.5 -8.0

Much like the Eastern Conference, the Western Conference Net Rating differentials closely resemble the Win-Loss Percentage ones, but have been included simply for the sake of comparison. 

Perhaps the most notable thing from both sets of Western Conference rankings is how it shows a shift in the balance of the conference. Last year, there was a big divide between a strong group of contending playoff teams and the lottery-bound ones, whereas this year, the conference got a bit more top-heavy. True title contenders like the Spurs, Warriors, and Thunder clearly got better, while the rest of the playoff teams dropped off and shortened the gap between them and the lottery teams, who mostly got better.