Midway through the 2012 Western Conference finals, after the Spurs had passed and cut the Thunder into a dizzy haze, Oklahoma City came to a collective realization that tipped the league’s balance of power: Holy crap! We are crazy athletic and long and tall, and we can overwhelm these guys if we just amp all of that up to 11!

Oklahoma City’s defenders took an extra step into the paint, clogging the middle on Tony Parker and Manu Ginobili drives, and forcing the Spurs to keep resetting the offense with kickout passes. Open guys would catch the ball, begin their shooting motion, and suddenly realize that a fast man with giant arms was running at them like a lunatic. They’d put the ball on the floor, blow by that first giant man, drive to the rim, and find four more giant arms waving around.

The Thunder didn’t shut down San Antonio over the last four games of that series, but they turned what had been a historically unstoppable offense on a 20-game win streak into a run-of-the-mill “good” scoring unit. That was enough, and the Thunder have owned San Antonio since, going 10-2 against the Spurs since losing the first two games of that series.

If the Thunder had a matchup edge, Serge Ibaka personified it. The dude is everywhere at once, and he has gotten steadier and smarter over the last two seasons. He unnerves anyone who approaches the rim, zooming from the foul line to challenge what appeared a half-second earlier to be an uncontested layup. He can switch out on Parker, contain a drive, and challenge Parker’s midrange shot. He barrels down on outside shooters, erases Russell Westbrook’s mistakes, and bothers San Antonio’s big men at the basket.

But Ibaka won’t be playing in the Western Conference finals.

The Thunder have other capable big men, but nobody who leaps and moves like Ibaka — nobody who covers space like him. They have two other insane athletes, and one of them, Kevin Durant, can slide to Ibaka’s power forward position. San Antonio’s Tiago Splitter is not a post-up threat, and the Heat played him off the floor in last year’s Finals by going small and taking their chances with a wing guy checking Splitter down low. Boris Diaw will have better luck than Splitter butt-checking Durant on the block, but the Thunder can live with that, and downsizing is a way to generate spacing for which the Thunder starters will be starved without Ibaka’s midrange jumper.

The Thunder should even think about starting smaller, especially with Caron Butler’s hybrid positionality on board now. But a change that big likely won’t come until later in the series. And the Thunder are most deadly going small with Ibaka’s rim protection at center. Stupid injuries.

There were reasons to downplay that 10-2 record even before Ibaka’s injury. A pile of players on both teams missed at least one of the games, but the absences hit San Antonio especially hard. Kawhi Leonard, acquired in a landmark draft-day trade with Durant specifically in mind, missed one game this season and most of another. Jeff Ayres was heavily involved. Diaw played small forward at one point. Marco Belinelli spent a lot of time guarding Durant, and Jeremy Lamb checked Ginobili. Westbrook missed one game, and the teams played just once after the Thunder acquired Butler.

So much has changed since the last four games of that 2012 series, a turnaround so abrupt it was almost jarring. You felt pity for those Spurs, aging and refined, the “play the right way” darlings of the league over 50 or so masterpiece games. Teams normally have time to understand their descent, to process the changing of the guard. The Thunder forced it upon San Antonio in a week, before anyone realized what was happening.

James Harden and his series-changing shots are gone, the Thunder left hoping a mishmash of replacements can add up to one superstar. The team’s offense has barely evolved under Scott Brooks. Thabo Sefolosha’s shooting has regressed, freeing teams to gleefully ignore two of the Thunder’s starters — and without Ibaka, perhaps three of them. Reggie Jackson has not lived up to his early-season promise, minus a few pivotal bursts.

Leonard is more developed on both ends, a balletic defender who poses an increased threat on offense — in the post, off the bounce, and as a one-man fast break. Danny Green isn’t green anymore, and the Spurs are deeper on the wing and at backup point guard, fine with going small alongside Oklahoma City.

Splitter and Tim Duncan logged just one minute together in that 2012 series. They’ve started together full-time since. San Antonio dreamed of getting double-barreled rim protection from the Splitter-Duncan pairing without compromising its spacing, even though neither is a threat to score outside 18 feet. It took years of work, but the Spurs have gotten there.

This was going to be a fight even with the Thunder at full health. And it’s an irresistible matchup — the polished veterans with so-so athleticism running a beautiful system against the league’s most athletic team, a group with such fearsome speed, individual scoring, and leaping ability that it doesn’t even require a system. Sometimes the easy narratives are right.

But they’re also simplistic. The Thunder have a system on defense: pack the paint, shut off the rim, use length to run back out at 3-point shooters. Nick Collison calls it “our version of a zone.”

It’s just that sometimes the system goes out of whack. Three or four defenders swarm to the basket when just two would do; Ginobili has four defenders surrounding him here, even though Splitter is the only threat near the basket and in Ginobili’s passing lane:

It’s a tribute to Oklahoma City’s activity that it can deflect these kinds of passes and recover in time to at least scare Leonard in the right corner.

Durant’s positioning on the right block during this Parker pick-and-roll is the precise extra rotation the Mavericks avoided in the first round, when they forced San Antonio (at least early in the series) to beat them with midrange 2s; Leonard got an open 3 here after catching Parker’s pass:

Sometimes a defender who should be “zoning up” between two enemy shooters gets enraptured by the action in the paint and chills in the wrong position:

The Thunder bigs love to attack pick-and-rolls beyond the 3-point arc, even though most of them are too slow to contain speedy point guards that far from the hoop. It’s a hyper-aggression that invites water bugs like Parker to split the defense or slip easy pocket passes to rolling bigs — provided Parker’s hamstring is really “fine”:

The Thunder turned the tide against the Clippers after Game 1 of the conference semifinals by dialing back these hard hedges. Defense with the Thunder is about leveraging their athleticism without letting it overtake them into chaos.

Westbrook’s hyperactive, foolhardy defense is a bad matchup for Parker’s constant motion. Westbrook loves to jump plays, but in the process, he lunges himself out of position against canny point guards who preface their moves with false actions. In his feverish recovery, Westbrook can run smack into picks:

And since he works his ass off to get back into position, he sometimes lets himself relax for just a second when he gets there. That’s death against Parker, who never really stops moving. Westbrook might think a play is contained, but Parker is already changing directions, darting to the ball from a different angle. There are no discrete first, second, and third actions with San Antonio. There is just action. Parker within the Spurs’ ecosystem might be an even bigger challenge for Westbrook than Chris Paul’s trickery.

That momentary relaxation can leave Westbrook far behind the play and give Parker a dangerous amount of airspace with which to work. There is a reason the Thunder have turned now and then to Sefolosha against the league’s wiliest point guards, including Parker.

Parker leaves Westbrook in the dust here by stopping on a dime, sprinting back toward a Duncan pick, and catching a pass from Green:

Parker has a giant head start as he preps to catch a pass from Splitter here:

Westbrook may spend some time guarding Green in this series, but when Ginobili replaces Green, the Spurs just get trickier. And giving heavy time to Sefolosha may cripple a Thunder offense now missing its third-best player — especially if Brooks is overly cautious about going small.

Sometimes, the only recourse is the hopeless reaching gamble:

Westbrook’s athleticism helps compensate for his bad habits. He can snag improbable steals and close airspace quickly enough to block a shot from behind. Those plays have a galvanizing effect on Oklahoma City. There is value in maniacal effort, even if bad fundamentals necessitate it.

Ibaka was the fail-safe. The Spurs are relentless in attacking any defense. They respect Oklahoma City’s speed, but they are not intimidated by it. They do not deviate from what they do. They just do it longer and in more creative ways, until they find something good.

Ibaka was the guy most likely to turn “something good” into “a dispiriting failure.” The Thunder have other good big-man defenders. Collison is always in the right position. Steven Adams has had his postseason moments. Kendrick Perkins bothers Duncan in the post and takes up space. Durant’s arms are like a sixth defender.

But it was the combination of Ibaka and all of those things, all of those other arms, that tipped the balance against San Antonio. He was the destroyer above the basket. Collison and Adams have foul issues that can be exposed over longer minutes. More time for Perkins is almost never the right answer to anything. Durant can only do so much.

The lane seemed so crowded with Ibaka, so off-limits, that it was unclear how much the Spurs could really play Splitter and Duncan together against this Thunder team. San Antonio scored just 88.3 points per 100 possessions against the Thunder with that duo on the floor this season, and though it fared much better last season, it seemed at times like the Spurs just didn’t have enough space to breathe.

Diaw helps as a big capable of shooting 3s and handling the rock up high, and the Spurs need a lot of him in this series regardless. He is a wild card against Oklahoma City’s small-ball lineups. The Spurs have at times stayed big against those Thunder groups with Diaw and a second big man, confident Diaw can slide his feet along with Durant on defense and overpower him at the other end. The emergence of Patty Mills gives San Antonio more options against smaller Thunder lineups that include two and even three point guards — Westbrook, Jackson, and Derek Fisher. The Spurs can go big or small, and, if they’re feeling really frisky, they can unearth Matt Bonner and hide him on a nonthreatening Thunder guard.

Again: This felt like a toss-up before Ibaka’s injury. The Thunder still have advantages upon which they can lean. Westbrook will post up Parker, and the Spurs have been unable to keep him from the basket. He is overpowering for Parker, too fast for San Antonio’s big-man help defenders. The Spurs have occasionally shifted Green or Leonard onto him, though that creates issues elsewhere, and they will need Leonard on Durant full-time. But Jackson, Sefolosha, and even Butler represent workable hiding places for Parker.

Durant will score, and he has toggled between harassing Leonard and Ginobili on the other end. Leonard’s burgeoning post game has not been a threat against the Thunder; he attempted just one post-up shot against them this season, per Synergy Sports. The Spurs can’t naturally switch Westbrook-Durant two-man actions like some other teams can.

The Thunder still have two of the 10 best players in the league, and a coach who has finally in these playoffs inched toward giving his best lineups a larger share of the team’s minutes. If you have those things, you have a chance — and perhaps a very good one.

But Ibaka encapsulates a lot of what makes Oklahoma City so dangerous to the Spurs. San Antonio is the league’s best team, but this has been a problematic matchup. Ibaka is the rim protector the Spurs have trouble overcoming and the third option who demands attention. He has had some seminal games against San Antonio — his 11-of-11 performance in Game 4 in 2012, a 25-point outburst last season, and four solid games this year.

The Thunder will have to scramble without him. Let’s be clear: The Spurs could have taken this series with both teams at #FullSquad levels of health. Hell, they might have taken it in fewer games than we’d expect. They are that freaking good, and sports are unpredictable.

But without Ibaka, it feels like they have a major edge.

SPURS IN SIX