Russell Westbrook is averaging a career-high 2.1 steals for the Thunder this season. (John W. McDonough/SI)

ByBen Golliver

Is it possible for a team to be regarded as the NBA's best and yet still be underrated? And just how many more years of improvement does a team have if it's gotten better every season since 2008?

Those are just some of the questions posed by this year's Thunder, who are an NBA-best 30-8 and sit atop a vast majority of the NBA Power Rankings you're likely to find around the Web. Oklahoma City has won four consecutive games and is 21-4 since the day after Thanksgiving, including three double-digit road victories already this month. The Thunder are prepared to deliver a whooping, any time, any place.

Because of strong starts by the Clippers and Spurs, and the hanging memories of the Heat's 2012 Finals triumph, one could argue that the Thunder's accomplishments actually haven't received enough attention. To date, their efficiency numbers suggest that they are one of the most consistently dominant teams the NBA has seen in the last decade, trailing only the 2007-08 title-winning Celtics and the 66-win LeBron James-led Cavaliers in 2008-09.

Net points per 100 possessions

An ideal basketball team would score every single possession and never concede a hoop. While there aren't any 100-0 blowouts in the NBA, measuring a team's net per-possession production is an intuitive way to understand how effective it is relative to the competition. By comparing a team's offensive rating, or how many points it scores per 100 possessions, to its defensive rating, or how many points it allows per 100 possessions, you can separate the teams that are truly hammering their opponents from those that are merely slipping by. In looking at things on a per-possession basis, you remove the element of pace to account for varied styles of play.

With the NBA's No. 1 offense and No. 6 defense, the Thunder are leading the league in net rating, scoring 9.8 points per 100 possessions more than they concede, according to Basketball-Reference.com. The 29-9 Clippers, ranked No. 4 on offense and No. 3 on defense, are just behind them, producing 9.7 points per 100 possessions more than they permit. The 29-11 Spurs are third at plus-8.4 points per 100 possessions. From there, it's a steep drop: The Heat are fourth at plus-5.4 points per 100 possessions and the Knicks are fifth at plus-5.2 per 100 possessions. To get a sense for the range involved, the 9-28 Bobcats rank last by this measure, giving up 8.9 more points per 100 possessions than they generate.

It takes zooming back to a decade worth of data to realize how impressive the Thunder -- and the Clippers -- have been this season.

The 2007-08 Celtics boast the top rating by this method, thanks to a stifling, top-ranked defense and an above-average offense. The Celtics won 66 games and went on to defeat the Lakers in the Finals. The 2008-09 Cavaliers, according to the numbers, were the best of the James-led teams despite a disappointing and surprising loss to the Magic in the Eastern Conference finals. That season, the Cavaliers' slow-down style posted the No. 4 offense and No. 3 defense and enjoyed 28.4 points, 7.6 rebounds, 7.2 assists, 1.7 steals and 1.1 blocks a night from James. The top 10 by this measure also includes the 2006-07 and 2004-05 title-winning Spurs teams and a 2007-08 Pistons team that made the Eastern Conference finals.

How are the Thunder doing it?

The easy answer is the offense, especially the day after Kevin Durant and Russell Westbrook combined for 77 points in a 12-point win at Phoenix (on the second night of a back-to-back, no less). No question, Oklahoma City's attack has reached new heights, even without James Harden. The Thunder's 112.7 offensive rating is the highest of the Durant era; that it should come in a year in which Durant is posting a career-high Player Efficiency Rating and making a serious run at the exclusive 50/40/90 shooting club is no surprise. Westbrook is averaging 22.2 points, 8.4 assists and 5.3 rebounds and his PER is an excellent 23.4, even if his shot has been a little shakier this season compared to last. Oklahoma City has seen growth from Serge Ibaka and smoothly incorporated Kevin Martin. The Thunder also excel in key offensive metrics: They are No. 2 in the league in free throws attempted and No. 3 in three-point percentage.

“We basically lost to Russell Westbrook and Kevin Durant,” Suns center Marcin Gortatlamented to the Arizona Republic after Monday's loss. “Those two guys were outstanding. … The pick-and-roll between those two is ridiculous.”

Indeed, the Thunder's offensive efficiency ranks No. 10 among all teams in the last decade, trailing only five years' worth of the Steve Nash-led Suns, the 2008 and 2009 Lakers, the 2009 slow-down Blazers and the 2008 Jazz.

A major benefit of looking at teams from a net rating standpoint, though, is that it forces you to consider all factors in judging a team. To wit, aside from the Thunder, none of the other top-10 teams in offensive efficiency appear among the leaders in net rating. Why? The run-and-gun Suns never cared much for defense and the Blazers and Jazz had defenses that were slightly above-average rather than elite. The 2008 and 2009 Lakers were the most balanced among the teams with elite offenses and, even though they finished just outside the top 10 in net rating, they have two Finals appearances and the 2009 title to show for it.

The obvious conclusion: Oklahoma City's defensive proficiency has gotten lost amid all of the Durant and Westbrook highlights. The Thunder's defense rates as the best of the Durant era, owing to a number of possible explanations. Most of the Thunder's rotation has been together for multiple years, the team has enjoyed excellent health again this season (no starters had missed a game until this week, when Serge Ibaka and Thabo Sefalosha both were sidelined) and individual defenders have improved.

Long one of the NBA's premier shot-blockers, Serge Ibaka (right) has further refined his game this season. (Layne Murdoch/NBAE via Getty Images)

One key theme on defense has been discipline. Westbrook is averaging a career-high 2.1 steals per game yet seems to gamble less and position his body more effectively. Ibaka, one of the league's premier shot-blockers, has fine-tuned his help defense, leaving fewer opportunities exposed behind him when he comes across the paint for a swat. Durant has appeared far more focused and concentrated on defense over the last few years, transforming himself from a minus- to a plus-defender. As a team, the Thunder seem more familiar in their pick-and-roll coverages and more committed to their perimeter rotations, although it's hard to quantify those extra-effort plays.

It's abundantly clear that they study opponent tendencies, too. In a grinding victory against the Blazers on Monday in which Portland shot just 36 percent, the pick-and-roll coverage from Westbrook and company limited the effectiveness of Rookie of the Year candidate Damian Lillard. On the game-deciding play, center Kendrick Perkins forced All-Star forward LaMarcus Aldridge to his left; Aldridge missed badly on a potential game-tying jumper and admitted afterward that he wasn't totally comfortable going left in that situation.

"That's one of the best young point guards in this league," Thunder coach Scott Brooks said of Lillard. "[Westbrook] did a good job of staying in front of him and we did a good job on his pick-and-roll plays. ... I thought his floor game and defensive game was at a high level. [As a team], I thought it was inspired, defensive basketball. It was one of our best defensive games of the year."

Continual improvement

Although Westbrook is known as one of the league's most passionate and emotional players, and Durant's in the midst of an image transformation that includes a "KD is not nice" campaign, make no mistake: There is nothing frenetic or unstable about this group. In eliminating the Spurs in the 2012 Western Conference finals, Oklahoma City seemed to beat San Antonio, long the gold standard for efficiency and consistency, at its own machine-like game.

"We've never lived by a stopwatch or a calendar," Oklahoma City general manager Sam Presti told ESPN.com after the Thunder eliminated the Spurs last year. "We've just tried to continually invest in the process of continuous improvement and let the results settle where they may by the quality of the work. There's really no finish line in terms of trying to continue to improve. It's a credit to our players and our coaches to embrace that."

Net rating helps quantify and visualize that goal -- and its proven results -- quite well. Consider: In Durant's rookie season, when the franchise was still in Seattle, the SuperSonics ranked last in net rating. The Sonics generated 100.5 points per 100 possessions and conceded 109.5, for a net rating of minus-9. How bad is that? That rating ranks No. 290 out of 299 over the last 10 years; only the absolute worst of the worst, teams such as the 2012 Bobcats, the 2010 Nets and the 2006 Blazers, have posted worse marks.

In every year since 2008, the Thunder's net rating has improved. In 2010, the first year the Thunder made the playoffs, Oklahoma City cracked a positive net rating for the first time. The team haven't looked back since, improving from very good in 2011, to great in 2012, to elite in 2013.

Here's a visual look at the Thunder's rise from 2008, when their minus-9 net points per 100 possessions ranked No. 290 out of 299, to 2013, when their plus-9.8 net points per 100 possessions ranks No. 3 out of 299.

The visual look at six seasons of play, with better results posted year after year, begs the question: If this year's Thunder are already among the best teams of the last decade, where might next year's be?

Can the Thunder maintain this level of play?

The NBA season hasn't quite reached its midpoint, and it goes without saying that it's significantly more difficult to maintain these numbers for 82 games than it is for 38. Still, Oklahoma City seems well-positioned on its track toward one of the most dominant seasons of the last 10 years. So do the Clippers, for that matter, who have actually posted their numbers against a more difficult schedule than the Thunder. It's quite possible that the two teams, in a race for the Western Conference's No. 1 seed and home-court advantage, continue to push each other to maintain this breakneck pace. Both teams have chips on their shoulders, both have the ability to run up large winning margins in a hurry and both have enjoyed relatively good health among their star players. Lulls are coming -- they plague everyone over such a long season -- but there are no obvious red flags or fluky reasons to explain the current bodies of work from these two teams.

Grizzlies