Brad Stevens is an after-timeout genius. We already knew this, which is why everyone in the Delaware Valley was quaking when the Celtics had the ball down one with eight seconds left in overtime in Game 3 against the 76ers.

They had every reason to be scared. Stevens drew up another beauty, setting up a lob pass from Marcus Morris to Al Horford for the clinching bucket.

How did we get to the point where the 76ers were fooled by this amazing play? Turns out, they were fooled by it twice.

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Let’s start by going back to regulation

With 26 seconds left and Boston down two, Marcus Morris was raring to take a contested 22-footer in the corner. Instead of letting that happen, Stevens called a mid-possession timeout to work his magic.

Brad Stevens BRILLIANT End of Game SOB to tie the game: pic.twitter.com/hOdp2aNXRJ — Half Court Hoops (@HalfCourtHoops) May 5, 2018

The Sixers came out with a lineup of Joel Embiid, Ben Simmons, Ersan Ilyasova, J.J. Redick, and T.J. McConnell. In these situations — late shot clock, sideline or baseline out of bounds — NBA teams usually switch every screen to prevent any one player from getting open. Stevens figured the 76ers would switch every screen, so he ran two different screening actions designed to get Embiid out of the lane.

First, Marcus Morris set a screen for Al Horford to get Embiid on Al. Instead of staying in the play, Horford went over to the opposite side of the court to screen for Terry Rozier, taking Embiid with him.

That meant Boston was essentially playing 3 on 3 with one side of the court wide open. Knowing the 76ers would switch, Jaylen Brown went to screen for Morris. But instead of setting the pick, Brown turned off Ersan Ilyasova’s back shoulder, just as J.J. Redick was about to switch onto Morris.

With the lane open, that was all it took to throw the lob to Brown.

The Sixers remembered that and were ready next time ... at first

With 8.4 seconds left in overtime, Boston had the same situation on the opposite side of the floor. Philly put Embiid on the inbounds passer (Morris), and was hip to Boston’s switching action with Horford and Jayson Tatum. Notice how Robert Covington and Ersan Ilyasova are on the inside shoulder of their men.

Nobody else really moved around, so Stevens called his final timeout. Even though the play failed, Stevens learned something. He saw that the 76ers would have no problem switching Robert Covington onto Al Horford, even if that was a size mismatch.

Once he saw that, Stevens called timeout. And that was because...

Stevens was really setting the 76ers up for this

BRAD STEVENS GENIUS End of Game Again: pic.twitter.com/mgJnJlOlKZ — Half Court Hoops (@HalfCourtHoops) May 5, 2018

After the timeout, Stevens noticed that Ilyasova was guarding the inbounder instead of Embiid. To account for that, Stevens had Terry Rozier run as far away from the hoop as possible while his other three players stacked together near the block.

Because the 76ers were switching everything as they did on the previous two sequences (a sensible call considering the like-sizedness of Simmons and Covington), Embiid was standing way out by the free-throw line, ready to pick up whichever Celtic raced out of the pack. That person ended up being Jaylen Brown, who sprinted as far away from the hoop as possible to take Embiid with him.

Meanwhile, Simmons hugged Tatum, the Celtics’ No. 1 offensive threat. Stevens figured that the 76ers would do everything possible to deny Tatum the ball.

There’s just one problem: this. And guess who got switched onto Horford in a spot when a size advantage suddenly mattered.

Here’s how you know Stevens planned this after looking at the previous play. Notice where Covington is standing in the above screenshot. He’s behind Horford, as a normal post defender would be. Fast forward a frame, and look where Covington is.

Knowing the entire back side was cleared out, and knowing that Covington would switch onto Horford to deny him the ball, Horford and the Celtics let Covington front him. They made him think he was doing his job. That opened up the easy lob over the top and the crucial bucket.

There was a school of thought that Horford was not the primary option on the play. Hopefully the above breakdown convinced you otherwise, but in case you need further proof, Matt Howard, one of Stevens’ players at Butler, provided it.

We actually ran, essentially, the play you saw last night a few times 7-8 years ago on late game or late shot clock side-out. People who don’t think Horford was the primary option proves the great design of this play. https://t.co/7znXDMuD3g — Matt Howard (@MHoward54) May 6, 2018

It takes a brilliant coach to exploit the 76ers’ defense twice on the same kind of play. It takes an even more brilliant coach to do it while making them think they solved the problem the first time around. As Horford told ESPN’s Cassidy Hubbarth after the game:

“Brad is a genius, man. Unbelievable. Sometimes he draws some stuff up and I look at him like, I didn’t think [you could do that].”

That’s Brad Stevens for you. Poor 76ers.