There always has to be an injury.
Last year, it was Russell Westbrook to go down in the playoffs, and now Serge Ibaka is expected to miss the rest of this season's playoffs with a Grade 2 left calf strain. In the regular season, Thabo Sefolosha missed about five weeks with his own left calf strain, and a Grade 2 strain generally requires 4 to 8 weeks of recovery. If the Thunder get really lucky and Ibaka pushes himself (which he probably shouldn't), he could return late in the NBA Finals. But that would imply they can make it there, and as if the San Antonio Spurs weren't intimidating enough already, the loss of Ibaka becomes another obstacle for the Oklahoma City Thunder.
What can the Thunder do next? If there is one positive, losing Ibaka isn't anywhere close to the death knell that losing Westbrook was last season. The Thunder still has the front court talent to succeed, but their margin for error has been slashed, and strategically, this entire series has changed.
Ibaka was the Thunder's defensive anchor, and from a league-wide standpoint, he was THE defensive model for any other shot-blocker or rim protector to try and emulate. He finished second in blocks per game this season with a 2.7 average, making it the fourth season in a row that he finished top-4 out of five years in the NBA. His absence leaves a gaping hole in the paint, one that provides the Spurs with more breathing room on offense against one of the league's best defenses.
Sample size alert – in the 144 minutes Ibaka played in four games against the Spurs this season, they were only able to shoot 42.3% and generate an offensive rating of 93.0 against him. In the 44 minutes of Thunder-Spurs matchups that he spent on the bench, those numbers skyrocketed to 51.4% and 120.8. The most striking on/off stat is, naturally, the difference in the paint as the Spurs shot 46.6% from within 5 feet while Ibaka was on versus 63.6% with him off.
Losing Ibaka's ability to protect the rim doesn't only mean that the Thunder will lose their best means to keep their opponent's field goal percentage at the rim low. It also means that they lose their greatest threat against teams that want to attack the paint. Against an offense like the Spurs' that executes so precisely with free-flowing ball movement and player movement, opposing players no longer have images of getting rejected by Ibaka in the back of their head.
With the weight of Ibaka's presence gone, it's going to feel like open season on the rim and that also means the Thunder defense will likely make up for the loss of Ibaka by reacting to attacks toward the paint, giving greater flexibility to the Spurs' outside shooters. Previously with Ibaka, the Thunder could stick tighter on guys like Danny Green and Marco Belinelli, enough to force them out of a three-point shot and into something like a midrange pull-up.
There's nobody on the roster that can replace what Ibaka offered, and that's a hard fact that we can knock out right away. Starting center Kendrick Perkins has had bright moments against the post onslaught of players like Zach Randolph and Blake Griffin, but the Spurs attack the paint much differently than the Memphis Grizzlies or the Los Angeles Clippers. Steven Adams has been great in these playoffs as a beast on the boards and a brute in the paint, but the Spurs are as well-engineered a team as any and will fully exploit the defensive inexperience that has already reared its head from time to time. Nick Collison is the Thunder's most cerebral defender and was a driving force in the Game 6 comeback win against the Clippers, but he's not a shot-blocker with head-over-hoop athleticism.
Perkins, Adams and Collison should offer enough to put a dent into the loss of Ibaka, though. Wherever they stick with a conventional lineup over going small (which Brooks has typically avoided in the starting lineup whenever injuries have struck, although lineups throughout the game are a different matter), it would make the most sense for Collison to replace Ibaka as the starter. Against the Spurs, who don't have an explosive run-and-jump athlete in the frontcourt like Blake Griffin, Collison's lack of shot-blocking ability should not be exploited. If all goes well, he'll be able to challenge Tim Duncan in the post and contain the pick-and-roll attack of Tony Parker while getting some help from Adams off the bench. It's not ideal, but hopefully it isn't an end-game scenario.
However, the most important way for the Thunder to minimize the damage done by an injury to Ibaka is to maximize what they can do on offense by trotting out small lineups with more offensive talent. Neither of Collison, Perkins or Adams can match Ibaka's catch-and-shoot consistency or touch around the rim. For a team that normally leaned heavily on Ibaka's ability to drag a big man out of the paint and finish pick-and-pops, the Thunder won't be able to do that with his replacements.
Small lineups with Kevin Durant as the nominal power forward aren't anything new. Brooks generally avoids starting them, but we've seen small-ball lineups in the regular season and even these playoffs without an injury to induce them. They're good lineups, and Brooks is well aware of that. Based on total plus/minus over the regular season, the Thunder's second and third best lineups saw Durant at the four accompanied by one big man and three guards (Caron Butler didn't make these lineups as a late-season signee, but for all intents and purposes, he's a guard when the Thunder go into these small lineups).
In a perfect world, Ibaka would be the one big man aside Durant. As one of the most athletic big men in the league, he's a one man interior defense and contributes on offense for good measure. The Thunder's two most used small lineups both featured Ibaka, as did their small lineup with the highest total plus/minus in the regular season (which wasn't one of the two most used lineups).
The Thunder are probably going to be relegated to running Collison or Adams as the lone big man in small-ball lineups, and honestly, that should be fine even if not ideal. Perkins doesn't fit as a center in small lineups, and it's probably for the better his minutes have been regressing overall lately. Small-ball lineups with Collison as the center, the second-most frequently used lineups, generally worked well in the regular season and should be fine against the Spurs. The main concern will be that Collison is only 6'9", leaving room for taller players like Tim Duncan or Tiago Splitter to take advantage. The Thunder will have to score enough on the other end to make up for it.
That's where the importance of Kevin Durant and the others come into play in replacing Ibaka's impact. Behind Durant and Westbrook, Ibaka averaged the third-most points for the Thunder in the regular season with 15.1 per game. Reggie Jackson lit up the Spurs for 21.3 points per game over four games. Going small will mean the Thunder have to maximize their offensive production with quicker and more dynamic lineups to force the Spurs to also go small. The best way to do this will be to stack two of Durant, Westbrook and Jackson into a simultaneous offensive attack (a pick-and-roll, a down screen-and-slip cut, etc.) with the third as a tertiary scoring option or facilitator. Combining your most skilled players into even simple actions will give defenses a lot to think about.
A Durant/Westbrook/Jackson/Collison or Adams lineup will be supported by a platoon combination of Thabo Sefolosha, Caron Butler and Derek Fisher, and it'll be important for those three to make their outside shots and command defensive respect away from the stars. Westbrook and Jackson are both inconsistent outside shooters, and the Spurs defense will willingly help off any of Jackson, Collison or Adams. If Sefolosha, Butler and Fisher can't command respect, then the offensive punch of a lineup built around Durant, Westbrook and Jackson's ability to score with the ball will be diminished.
It's still not a great shot at victory against the Spurs, who have the tools to shut down the Thunder's best attempts to get past an Ibaka injury. Kawhi Leonard is getting the Durant assignment no matter what, and losing the ability to put KD alongside Ibaka in a small lineup means the Spurs will generously deny and double-team KD in the post with a big man in the same way that the Clippers did with Chris Paul and DeAndre Jordan.
On a similar note, the Spurs will sink their big man way back into the lane against pick-and-rolls led by Westbrook or Jackson (a downside of losing a pick-and-pop option like Ibaka) and do everything they can to eliminate the disadvantage of the Thunder going small with that one big man. Tim Duncan, Tiago Splitter and even Boris Diaw (known as "the LeBron Stopper" in selective parts of the world) are all highly intelligent defenders and bulky or long enough to contain dribble penetration.
On the other end, the Spurs are perfectly capable of matching the Thunder by going small themselves. Tony Parker, Manu Ginobili, Kawhi Leonard, Danny Green, Marco Belinelli and Patty Mills combine for a deep platoon of perimeter players with a dangerous mix of dribble penetration, shot creation and outside shooting. Boris Diaw is the type of versatile two-way player that can be deployed alongside a more conventional big man even against a small lineup, and Tim Duncan is Tim Duncan. Gregg Popovich's masterful deployment of his roster makes it fully possible of matching every look the Thunder have to throw at them.
Unsurprisingly, it all comes back to the Thunder's star talent and whether or not that talent can dominate all other factors, including fit and matchups. As Durant and Westbrook goes, the team goes – everything else is secondary. In Game 6, the comeback effort made without Ibaka was supported by Collison, Jackson and Adams. They were critical without a doubt, but there wouldn't have been a comeback effort at all if Durant and Westbrook weren't there to propel the team back into it. It sounds too simple, but them's the facts.
We'll see if the Ibaka injury leaves the margin for error too tight for the Thunder to power past. It'll be important for Brooks to make the most of his decisions with his role players to maximize what Durant and Westbrook can do, but the Spurs are good enough to neutralize any impact the role players try to make and then work their way up to dulling the Thunder superstars. Everything the Thunder do will have to be done even more carefully than usual, and that goes double when they play against the Spurs. Don't rule out the Thunder from winning the series just yet, but know this: the Ibaka injury makes a hard task even harder.