We've heard a lot of talk about defense over the last couple of days. Throughout Game 1, the Celtics did a masterful job of coaxing the Sixers into half-court matchups that favored Boston and resulted in wide-open shots.

Let's take a look at two plays that highlight what, exactly, went wrong for the Sixers in Game 1, and the solutions that they will need to come up with in Game 2.

Play 1

Below is a wide-open three-pointer by Terry Rozier late in the second quarter, after Al Horford beat Joel Embiid on a drive, which prompted Robert Covington to leave Rozier.

Here it is in real time:

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Sixers GIF - Find & Share on GIPHY

And, in slow motion:

At the start of the play, Embiid is in the paint, protecting against a potential drive by Rozier, who has the ball and is guarded by Covington. Embiid's man is Horford (42), who is two passes away from the ball. Horford drops back to the three-point line and Rozier throws a skip pass. Embiid scrambles to get out on Horford to contest a potential three-point shot, and Horford uses the big man's momentum against him, driving to the hoop.

In the side-by-side sequence below, you can see what happens next:

Covington drops into the paint to provide help on Horford, which leaves Rozier open for the spot-up three.

This is the kind of breakdown the Sixers have undoubtedly spent the last couple of days attempting to troubleshoot. The first and most obvious solution, it would seem, is for Covington to stay within close-out distance of his man. Embiid might be beat, but he is still in position to contest a Horford layup, and a contested Horford layup has a lower Expected Value than a wide-open Rozier three-pointer.

Play 2

Below is a play that ends up as a Rozier three-pointer. Rozier is in the lower right corner of the screen, away from the ball.

Shane Larkin throws an entry pass to Marcus Morris, who has the outsized Marco Belinelli sealed off on the left wing:

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Animated GIF - Find & Share on GIPHY

Let's freeze it there. In the image below, you'll find the important players.

Green boxes: Embiid is minding Horford while watching the ball, no doubt feeling an impulse to protect the rim.

Purple star: JJ Redick sees that Morris has the smaller Belinelli sealed off from an open baseline.

Yellow circle: Rozier, whom Redick is guarding.

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We'll pick the play up there. As Redick rotates over to provide help to Belinelli, Horford cuts to fill the hole in the defense. Rozier, meanwhile, comes up from the corner to replace Horford at the top of the three-point line. Embiid gets sucked in by Horford's motion, leaving Rozier wide open for the catch-and-shoot.

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Animated GIF - Find & Share on GIPHY

In Game 2, it will be interesting to see how the Sixers defend this kind of sequence. How do you avoid getting caught in this kind of matchup? Once Morris has the ball, Simmons can't leave Jayson Tatum open in the corner. But even if Embiid prevents Rozier from shooting, and Rozier makes the extra pass to Tatum, the Celtics have Horford in position to post up on Redick on the low block.

The answer, I assume, is to avoid getting Morris matched up on Belinelli in the first place. Let's go back to the very start of the set. In the screenshot below, you'll see Dario Saric guarding Morris in the yellow box. In the green box, you'll see Belinelli guarding Larkin.

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In the clip below, you'll see Morris come across the court to set a screen on Belinelli. Saric switches onto Larkin, while Belinelli stays with Morris.

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Animated GIF - Find & Share on GIPHY

The switch:

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Animated GIF - Find & Share on GIPHY

The complicating factor is that Morris doesn't actually set a screen. Instead, he goes to the basket. I assume the answer is for Belinelli to go over top of any screen and Saric to stay with Morris.

The long and the short of it: Brad Stevens is a hell of a coach, and he coached a hell of a game. It's on Brett Brown to counter, and it's on his players to execute. It'll be fascinating to watch.