If the Thunder had kept Harden—the 2014-15 MVP runner-up who is in the midst of another impressive individual campaign, even if the Houston Rockets have slipped—they'd have three of the league's 10 best players: Harden, Russell Westbrook and Kevin Durant. No team has a Big Three quite like that.
The Thunder famously traded Harden, Cole Aldrich, Daequan Cook and Lazar Hayward to the Rockets for Jeremy Lamb, Kevin Martin and a trio of future draft picks, favoring the upside of Serge Ibaka and financial flexibility over re-signing Harden to a hefty extension.
Martin didn't last long in OKC, and Lamb now plays for the Charlotte Hornets. The draft picks haven't turned into anything more than Steven Adams and Mitch McGary—neither on par with Harden.
Still, that doesn't actually make the Oct. 27, 2012 deal a mistake.
The Ibaka Impact
The financial landscape of the NBA changes so quickly and drastically that it's tough to call the Thunder's dilemma in 2012 an either-or situation, even if keeping both Harden and Ibaka would've eventually triggered the repeater tax.
OKC claims it was forced to pick between the two after the shooting guard rebuffed a four-year, $55.5 million offer, but only because the small-market organization was unwilling to pay the steep luxury-tax penalties that would've resulted from holding on to everyone.
As Zach Lowe explained for Grantland shortly after the swap, league insiders were split on whether OKC had chosen correctly:
Both sides forced each other into a choice, and the Thunder have chosen Westbrook and Ibaka over Harden...There is a wide range of opinion around the league about whether the Thunder have chosen correctly on either count. Any of the three paths is defensible, but the Thunder have taken a risk in dealing a proven All-Star-level player and betting on Ibaka developing into that kind of player. But it's an understandable one, given the skill overlap between Durant, Westbrook, and Harden, and the fact that none of those three is a proven plus perimeter defender at this point.
In May 2014, he clarified, "I estimated that a minority of NBA executives with whom I spoke—maybe 20 percent—thought the Thunder had chosen incorrectly."
Ibaka hasn't turned into a consistent All-Star, much less an MVP-caliber contributor. In fact, he hasn't represented the Western Conference even once during his career. Midway through the 2015-16 campaign, he's averaging just 13.0 points, 6.9 rebounds and 2.1 blocks while shooting 49.2 percent from the field and 38.5 percent from beyond the arc.
Still, he's become invaluable to OKC's system. His floor-spacing and rim-protection skills fill holes that would have otherwise grown into yawning chasms. In a vacuum, Ibaka can't come close to matching up with Harden, but Ibaka's impact remains invaluable.
According to NBA.com's SportVU data, Ibaka is allowing opponents to shoot only 42.2 percent at the rim while challenging eight shots per game. Only Nick Collison (42.7), Steven Adams (46.2) and Andre Roberson (49.4) force opponents into sub-50 percentages.
Could the Thunder have found a rim-protecting big? Sure—but only from another draft-day miracle or a lucky hit on a devalued free-agent veteran. Could they have landed a floor-spacing power forward? Absolutely.
But getting both in a single package would have been nearly impossible.
Only a Single Basketball
The old NBA cliche remains true as ever: There's only one basketball. Sharing it between two high-usage scorers is already tough enough.
"We've got guys that can score. We've got two guys on this team that can get a bucket," Durant recently told ESPN.com's Royce Young. "There's going to be times we gotta iso, there's going to be times we gotta be aggressive to look for our shot to make a play."
Westbrook and Durant are essentially forced to alternate possessions and duke it out for alpha-dog status during crunch-time situations.
Remember, Harden was a sixth man in OKC. Prior to the trade, he'd made a grand total of seven starts during his three professional seasons. Many of his minutes came when Westbrook and/or Durant needed a breather.
But keeping Harden on the bench for much longer would have been nearly impossible. Sharing the ball between three elite scorers was a migraine waiting to happen.
"You can make the argument that the Thunder had the best young PG, SG and SF in the NBA at the same time," Jonathan Tjarks argued for RealGM last January. "That sounds great on paper, but it’s not a very balanced roster. That's like a team with the best QB, RB and WR in the NFL—they still wouldn't win without a good offensive line. Star-power isn't enough."
Harden might have been forced to maintain a reduced role. With fewer touches, Durant might not have developed into a dominant playmaker with ridiculous scoring chops. Westbrook might not have blossomed into the top-five player he is today.
Look at the usage rates each enjoys in 2015-16:
The Thunder are the only team in the NBA with two players in the top 12. If Harden were still around, in theory, they'd have three in the top 12—two of whom are in the top three.
That just doesn't work. Something would have to give, but what?
Thunder Are Still Pretty Darn Good
The Golden State Warriors and San Antonio Spurs are a historically elite duo, and the Thunder aren't far off. With 35 victories in their first 48 outings, they're on pace to finish the season with 60 wins. That's actually a lower total than the underlying metrics would project.
Based on the 1,345 teams that have completed NBA seasons, there's an extraordinarily strong relationship between net rating and wins—prorated to 82 games to account for lockouts and the shorter seasons of the past:
Maybe—maybe—the league's No. 2 offensive rating would be better if Harden were still in town. But with Adams and Ibaka then potentially playing for another squad, could the Thunder still have the No. 13 defensive rating in the NBA? That's doubtful even before we factor in the minutes allotted to the bearded sieve and hope his defensive apathy isn't contagious.
Did the Thunder make a mistake by trading Harden?
Given the level the Thunder have reached at full strength, it's hard to question the big move that led them to this point.
Adam Fromal covers the NBA for Bleacher Report. Follow him on Twitter @fromal09.
Unless otherwise indicated, all stats are from Basketball-Reference.com or Adam's own databases and are current heading into games on Jan. 29.