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The Boston Celtics stunned the Philadelphia 76ers on Saturday night in one of the best games of the regular season. In the waning seconds, Jayson Tatum hit a 3-pointer to give the Celtics a 110-107 lead, which proved to be the final score after Joel Embiid's made three-quarter court heave was ruled to have come after at the buzzer.

Down by 15 in the third quarter, the Celtics turned the game around and briefly led by double-digits in the fourth. But after Embiid led a comeback, the game was tied at 107 with 10.8 seconds remaining. The Celtics' first attempt to find a game-winner was cut short by the Sixers using their foul to give. 

That gave Celtics head coach Joe Mazzulla a chance to call a timeout and draw up a different play. He decided to go with an old favorite, a sidelines out of bounds set that he's used earlier in the season, and which he admitted postgame was stolen from Brad Stevens. Let's take a closer look at how the Celtics were able to free up Tatum for the game-winning shot. 

Most of the time in late-game situations like this one, a team will simply clear out and let their best player isolate on the perimeter. But while that's the safest option because it usually guarantees the worst-case outcome is overtime, it rarely leads to the best looks. Even for the most gifted offensive players, it's hard to score against a set defense that knows exactly what you want to do. The Celtics have learned as much countless times over the past few seasons. Movement, both ball and man, that gets the defense shifting and unsure of itself, is much harder to guard, as this play showed.

The play begins with Tatum deep in the backcourt, Jaylen Brown in the far corner and Marcus Smart and Al Horford near the 3-point line. This alignment spreads the floor to an incredible degree and gives the Sixers all sorts of things to worry about. 

Celtics spread the floor and start with Tatum deep in the backcourt

As Derrick White gets the ball from the ref and initiates the play, Horford sprints to the opposite corner to interchange with Brown, while Smart breaks towards midcourt to receive the pass. Tatum, meanwhile, begins to break towards the basket. There are a lot of moving parts here for the Sixers to read instead of just keying in on one guy with the ball.

The Celtics get the ball in to Smart, while Tatum breaks for the basket

The timing for this next part is crucial, and the Celtics get it just right. As Smart turns, Tatum is already in a full sprint, so the Celtics point guard can feed a bounce pass to his star man on the run. Now, Tatum has the ball going downhill against a rotating Sixers defense instead of trying to break them down from a stand-still position. 

Tatum catches the ball on the run

In a perfect world, the spacing and movement would give Tatum a free path to the basket. That's just what happened earlier in the season when the Celtics ran this same play against the Cleveland Cavaliers and Tatum dunked on Jarrett Allen

Here, however, Embiid recognizes what's happening and rotates over into the paint. That forces Tatum to pull up, but because Melton was sprinting alongside him, he can't stop in time and Tatum creates plenty of space. White is also left all alone on the wing due to Embiid's rotation, and Tatum could have made the extra pass. 

Embiid's rotation forces Tatum to pull up, but he still gets a clean look

But with such little time remaining and a clear look at the basket, Tatum made the wise decision to take the shot. He caught nothing but net. 

The Sixers had burned a bunch of timeouts trying to stop the Celtics' early fourth-quarter surge and had none left at that point so their only hope was to inbound it quickly and throw up a prayer. Embiid's was answered, but a split-second too late. His one-hand 67-foot heave from inside the 3-point line dropped through the net and sent Wells Fargo Center into hysterics, but the celebrations were cut short when the replays clearly showed the ball was still in Embiid's hand when the red lights came on. 

Tatum had a rough night overall. Though he put up 18 points, 13 rebounds and six assists, he also had five turnovers and shot 7 of 17 from the field. But when the game was on the line, he made the plays that mattered most. Including his game-winner, he either scored or assisted on the Celtics' final 11 points. 

"I told my teammates, told Grant [Williams] coming out of that timeout, 'game time,'" Tatum said. "Terrible game, but way to figure it out."