With one trade, the most tested starting lineup in the NBA broke up.
Kendrick Perkins, Kevin Garnett, Paul Pierce, Ray Allen and Rajon Rondo started 221 games together for the Boston Celtics, including the postseason, easily more than any other unit in the NBA over the past four seasons.
Together, they boasted a 128-46 regular-season record and were 30-17 in the postseason, according to the Elias Sports Bureau.
Through almost four seasons, they shared the court for 4,349 minutes. In that time, the Boston Celtics outscored their opponents by 1,102 points.
That era ended Thursday when Perkins was shipped to Oklahoma City, a move that leaves major questions on defense.
While Rondo orchestrated the offense and the Big Three provided the scoring, Perkins garnered accolades for his intangibles: grittiness, intimidation and defense. It's far more difficult to gauge a player's effectiveness on defense, an area in which typical stats such as blocks and steals don't provide a proper measure.
So just how valuable was Perkins to the Celtics' defense? Let's focus on the post, where Perkins did most of his prowling on defense.
In the previous three seasons, the Celtics' post-up defense ranked either first or second in the NBA in opponent points per possession. This season, with Perkins missing 43 games, Boston has dipped to fourth.
In that span, Perkins established himself as an elite post defender. He ranked third in both 2007-08 and 2008-09 in points allowed per play in post-up situations. Last season, he was sixth.
It's hard to find any scenario in which the Celtics have improved their post defense with this move.
Yet, the Celtics might still need to contend with elite post players in the Eastern Conference.
According to Synergy Sports data, Dwight Howard has scored 656 points when posting up this season. That's nearly 200 more than the player with the next most (LaMarcus Aldridge at 469). Meanwhile, Amare Stoudemire is putting up 1.12 points per post-up play, third best in the NBA behind Nene and Dirk Nowitzki.
Without Perkins, how will the Celtics manage against teams with traditional post threats?
Perkins was the Celtics' best answer for Howard, winning the battle in the post. Since 2007-08, Howard is averaging 0.89 points per play when posting up and shooting 48.9 percent. But against Perkins, those numbers plummet to 0.62 PPP and 34.8 field goal percentage. Already one of the best post defenders in the game, Perkins only gets better against Howard.
Compare that to the current post defenders on the Celtics' roster. In that span, Howard is averaging 0.81 points per play, while hitting 52 of 117 shots (44.4 percent).
Will this group be able to stop Howard? It's worth noting that he scored only six points against the Celtics on Christmas Day, a game in which Glen Davis played almost 40 minutes.
But the concern should extend beyond Howard. Opponents post up on the Celtics less often than against any other team in the NBA. Will this change without Perkins looming in the paint?
Nenad Krstic won't make anyone forget Perkins, especially on the boards.
For the past three seasons, Perkins -- not Garnett -- has been the Celtics' top rebounder. In that span, he has averaged 13.3 rebounds per 48 minutes, compared to Garnett's 12.8. Meanwhile, Krstic is hauling in only 9.8 rebounds per 48 minutes this season, which puts him on par with the recently departed Semih Erden.
There were plenty of factors that went into this deal, including Perkins' impending free-agent status. Injuries created a dire need for depth on the wing, and Jeff Green should provide that going into the future.
But for all the positives associated with the trade, there's no way to view it as a net gain for the Celtics' post defense. That doesn't necessarily spell doom for Boston, though.
Keep in mind that the Celtics were 33-10 without Perkins this season, the best record in the East.
In the end, it all comes back to Garnett's defensive presence.
Over the past four seasons, Perkins was plus-13.0 points per 48 minutes when on the court with Garnett. But without him, Perkins was minus-2.1 points per 48 minutes.
Now another Boston center gets to feed off KG. While Garnett leads the NBA in plus/minus per 48 minutes at plus-13.0, Shaquille O'Neal is right behind him at plus-12.5. Perkins, by contrast, is plus-6.3 through 12 games.
Shaq is still a defensive force down low. Opponents are shooting just 32.4 percent against him and averaging 0.70 PPP in post-up situations, according to Synergy.
Even with his 39th birthday coming up March 6, O'Neal is still a far more dynamic offensive threat than Perkins has ever been. If healthy (a legitimate if), O'Neal more than capably fills the post on both ends.
Consider the evidence: The Celtics' four main starters are plus-18.2 points per 48 minutes when joined on the court by O'Neal. In 12 games with Perkins, that's just plus-13.0.
In fact, the best plus/minus per 48 minutes for those four with Perkins came in 2007-08, when they were plus-17.7. In other words, the group has been doing better with Shaq than it ever did with Perkins.
Ultimately, that's the gamble. With the trade, the Celtics are counting on Shaq to get (and stay) healthy for the stretch run. The Celtics took a risk by breaking up their core but seem likely benefit in the short term.
The true test might come in the postseason, particularly if Dwight Howard looms in the paint.
Jeremy Lundblad is a researcher with ESPN Stats & Information. He provides statistical analysis for ESPNBoston.com.