It's a set that is typically run by the starters, with Rajon Rondo orchestrating things as usual. Normally, Rondo and Kevin Garnett start on the left side of the floor while the other three Celtics stand side-by-side-by-side on the right wing. When the play begins to unfold, Rondo and Garnett engage in a pick-and-roll (or pick-and-pop) on the left side, while the other three players simultaneously break to different spots on the floor. The center charges straight to the basket, while the small forward either hovers around the right wing or darts to the top of the key, and the shooting guard rotates down to the right corner.
I've deemed it the "horde play" because of the small gathering of players on the right wing. In a game so predicated on floor spacing, it's incredibly rare to see three teammates stand so close to one another for the sake of a single play. We're not the only ones who've noticed this particular set, as Jay Ouellette and our friends at Red's Army have acknowledged it in the past. Jay refers to the play as the "2-3 arc play" due to the way the players assemble on the court, and, in previous posts, has done a great job of using video to illustrate the sets.
The play is an effective one because it can create so many different looks for the C's on offense, while bringing about utter chaos for the defense. Ideally for the offense, the play would result in an easy layup for either Garnett or Rondo, but that depends largely on how well the defense can contain their pick-and-roll action. A wide open mid-range jump shot for Garnett is never a bad third option, but if that side of the floor proves too clogged, Rondo still has at least three other options to consider.
Rondo's ability to slice through the lane is no secret, which makes him ideal for this play. He can weave through the unsettled defense, and easily find the center, who should be diving to the rim by the time Rondo got into the paint; the small forward, who should have either flared to the top of the key or hovered around the right wing; and the two-guard who most likely has rotated down into the right corner.
The following video shows the play from a few seasons ago. Rondo strolls to the left side, and while Garnett comes over to set the screen, Ray Allen drops to the corner, Glen Davis makes his way into the lane, and Paul Pierce stays beyond the 3-point line. Rondo gets over the top of the defense and gets Davis the ball with solid positioning around the basket. Thanks to a befuddled Antawn Jamison, Davis only needs to utilize a simple left dribble drive to the opposite side of the rim to secure a layup.
In another example, the same pick-and-roll action between Rondo and Garnett happens on the left side, only this time, when Rondo gets around Chris Bosh, LeBron James is forced to help, giving Rondo enough time to feed Pierce for an open 3-pointer on the right wing. It's worth noting that Pierce has a tendency to hang around the right wing more, as opposed to flaring to the top of the key for a similar 3-point option.
Our final example shows how easily this play can generate a layup for the center crashing to the rim. The Grizzlies defend the pick-and-roll pretty well by initially bottling Rondo up on the left wing. But thanks to some quick and clever passing between him and Garnett, the basic makeup of the play is still in the works when Rondo heads to the basket on the left side. Davis crashes to the hoop as he's supposed to, and Rondo rewards him with a quick feed that gives way to an easy layup.
As you can see from the video examples (more can be found in a previous post by Jay over at Red's Army), the play is designed to bring about multiple options for the offense, which plays right into Rondo's hand as a creative distributor. The play also works for Boston because, beyond Rondo, the C's have a host of capable passers, including Garnett and Pierce. Despite each player having a set place to roam to when the play begins, it still requires the players to use their instincts to find the best option possible.
It's been tough trying to figure out when exactly Rivers chooses to utilize the play. There doesn't seem to be any set pattern in place, perhaps because the C's don't want to risk an opponent catching on too quickly and devising a defensive scheme to try and combat it. But it's certainly an effective play, and, as alluded to in Tuesday's Summer Forecast entry, Rivers shouldn't be afraid to incorporate it when the C's are fighting through one of the dreaded fourth-quarter scoring droughts that have hindered them in seasons past.