Since taking over as the Boston Celtics head coach to begin the season, Joe Mazzulla has presided over a significant change to how the Celtics go about their offensive execution. A “never say die” attitude from the three-point line, lots of five-out possessions, and a few plays that we see run multiple times per game.
Outside of the sheer volume of threes the Celtics are shooting these days, one play that has become synonymous with Mazzulla ball is the ‘stack’ action. Put simply, the ‘stack’ is when an action involves two screens — an on-ball screen and a back screen set on the first screener's defender.
In fact, the only thing that separates the Spain pick-and-roll and the stack action is what the second screener does after making contact with the screen recipient. However, it’s also worth noting that a Spain pick-and-roll can also be known as a stack action, as it’s essentially just a variation of the play.
It’s something that could create some headaches for the Philadelphia 76ers when the two teams face off against each other in the second round of the playoffs. Furthermore, the stack action is something that has proven successful for the Celtics when facing the Sixers. Below is each time they ran a stack action during their February head-to-head.
This first clip illustrates how Mazzulla likes his team to get into their stack actions early in games as they search to create confusion on the perimeter. It forces the defense to make multiple decisions at the same time. In this example, Al Horford is the ball screener, while Jayson Tatum sets a back screen on Derrick White.
As the action unfolds, White drags his dribble towards the sideline, taking Joel Embiid and PJ Tucker with him; Tatum flares out to the strong side wing, ensuring Al Horford has space to pop into on the weak side.
Just two possessions later, the Celtics went back to their stack action, this time running a ‘stack turn,’ where Derrick White turns into the back screen. It’s White’s back screen that opens up the space for Tatum to attack the rim, taking Embiid out of the possession and limiting his ability to provide nail help with a stunt toward the ball.
Here is the stack action again, early in the second quarter, with Sam Hauser operating as the back screener. What’s interesting in this play is how Hauser’s screen happens within the flow of the play, thus tagging Robert Williams’ defender while simultaneously hampering the closeout onto Malcolm Brogdon on the perimeter.
This time, it’s Jayson Tatum’s clear out to the weakside slot after setting the back screen, which creates the driving lane for White to exploit, resulting in a high percentile shot around the rim.
Another stack action, with Robert Williams clearing out from the strongside to once again create the gap for White to exploit on his way to the rim.
When you’re having so much success with a specific action, and the entry to that action is so easily recognized, it makes sense that you will sometimes set up the alignment as a decoy, which is what happened above. Tatum operates as the ball screener, with Williams lining up in the back screener position; however, rather than setting an actual screen, Tatum initiates a ghost screen (a non-contract screen followed by a flare into space on the perimeter.)
Interestingly, this action was the first one that started with a stack alignment that didn’t end in a bucket.
With a playoff series between these two sides looming, it would be fair to assume that Boston will look to create scoring opportunities using their ‘stack’ action in the early games before incorporating some variances into the play call to keep Doc Rivers and the Sixers defense on their toes.
In just one game, Boston ran this play six times, finding success on five of those occasions, and you know what they say, ‘if it ain’t broke, don’t fix it.”