From the open tip it was clear: The Boston Celtics had a plan. They executed it. And, man, did it ever work. As statements go, the Celtics made a loud one by dominating the Bucks in every way in a 112-90 Game 1 victory on Sunday. Kyrie Irving was splendid. So was Al Horford, who, along with an army of on-point helpers, taught Giannis Antetokounmpo a playoff lesson. You just could not have asked for a better Game 1 for the Celtics. It was close to perfect. And the thing is: It feels sustainable.

The basic tenets of this series are not going to change. The Celtics are going to get good looks from the perimeter because of the way the Bucks drop defensively in the paint, and on Sunday they made them -- 53 percent from the field, 41 percent from 3. If you think they'll stop making them, fine. But they're going to keep getting them.

On the flip side, Giannis ran into a defensive wall. It's not to say he can't eventually break through it in this series. But the wall isn't going anywhere. Back in November, here's what a league scout told CBS Sports about one of the problems Milwaukee was going to face in the postseason:

"I feel like Milwaukee is going to win a ton of regular-season games but be a disappointment in the playoffs. Nobody can guard Giannis, but [in the playoffs] they're going to have five guys basically defending him. Everyone shading, walling him off. He's going to be so frustrated. You just can't barrel through everybody every time in the playoffs. So now you're relying on the Khris Middletons and Eric Bledsoes to make a lot of shots."

This played out to the letter. Giannis was constantly surrounded by bodies and walled off in transition and stymied at every turn by Horford in the half court, and the shooters didn't provide the necessary release valve: Khris Middleton, Eric Bledsoe, Brook Lopez, Sterling Brown, Ersan Ilyasova and Pay Connaughton were a combined 13 for 48 from the field including 6 of 26 from deep. Add in the 7-for-21 showing Giannis turned in, and the Bucks shot 34 percent as a team.

Look how on point Boston's defense was from the start. This baseline spin off the back-down post is a go-to move for Giannis, but Horford does his homework. He anticipated the move, showed as a helper to cut it off, and forced Giannis to back it out and take a long jumper.

When Giannis attacked downhill, look at the bodies ready to surround him at the rim as Horford just straight-up stones him:

In the half-court, the Celtics were set for Giannis every time. He ran into wall after wall and Horford just flat-out muscled him with three blocks to go with 12 boards. Horford, and by extension the Celtics, owned the paint, which, of course, is what the Bucks are used to, and in fact dependent on, owning themselves. The Celtics outscored Milwaukee 38-26 in the paint, a disparity that holds exponential weight considering the way each team is equipped to attack.

The Bucks have the most dominant at-the-rim scorer in Giannis, plain and simple. Him getting in deep and either finishing or making defenses collapse off shooters, or at the least the threat of him doing so, is the foundation of every advantage Milwaukee has milked this season. If he can't do it consistently in the half-court against Horford and his pack of helpers, the Bucks have to get out into transition. But even when they did that on Sunday and Giannis had the ball in the open floor with a head of steam, this is what he faced:

This is the problem when you can't shoot (yes, I'm aware Giannis hit 3 of 5 from 3-point range, but if you think the Bucks are going to beat the Celtics with Giannis taking and making 3s, I don't know what to tell you). Russell Westbrook faced the same thing against Portland. John Wall has faced this for years in the playoffs. Ben Simmons got schemed almost entirely out of fourth-quarter minutes against Boston last season. Giannis is probably better than all those guys, but heck, we've even seen LeBron be forced into a more perimeter-oriented game by set defenses lying in wait for his penetration. It's tough. Like the scout said, you can't expect to just go through a brick wall every possession every game for an entire series.

This isn't to suggest Giannis isn't going to get it going in some capacity. Milwaukee will adjust. It'll try to get in transition more, but that starts with getting stops, and that brings us to another problem for the Bucks: Their defensive principles don't particularly line up with defending the Celtics. They drop and protect the paint at the expense of giving up 3s: The Celtics made the sixth-most 3s in the league this season. They made 13 on Sunday at over 41 percent, and they got a lot of good looks that they simply missed. If those start to go in, forget about it.

Meanwhile, nobody on the Bucks can guard Irving, who finished with 26 points, 11 assists, seven rebounds and a team-high plus-20 in his 33 minutes. He shot 2 of 5 from 3-point range. He shot 57 percent overall -- 12 for 21. He was brilliant. He controlled the pace, got in the paint and found teammates, and beautifully picked his spots to attack as a scorer. Oh, and apparently he's Kobe Bryant in the post now.

Here's a fuller look at Kyrie's wizardry in Game 1:

Meanwhile, the pick and pop for Horford is going to be open all series. Boston started Marcus Morris instead of Aron Baynes for two reasons: One, Morris is a primary defender for Giannis. And two, and perhaps more importantly, without Baynes on the floor Lopez is forced to guard Horford, and that's a no-win for Milwaukee. Either Lopez, or Giannis when he's the big, comes out on the perimeter to stop Horford from deep and and the mid-range on the pick-and-pop, in which case the lane is open, or the Bucks do their normal drop routine and Horford peppers jumpers all game. In Game 1, it was a lot of the latter:

Indeed, it was all working for the Boston on Sunday. Gordon Hayward was getting in the lane and finished with 13 points. Jaylen Brown was aggressive and finished with 19 points on 8-of-14 shooting. Morris and Terry Rozier combined for 20. The key is that they all got into the paint. The Celtics have to keep doing that, because that's what makes the Bucks sink those defenders in. If they decide to start creating for themselves on the perimeter without penetrating the paint first, or pulling up too early in the shot clock, Milwaukee's dropping tactics won't be so exposed.

But right now, Boston looks great, man. I picked Milwaukee in seven simply of the Giannis factor, and I think a lot of people did the same. Obviously that can still happen. But a lot was exposed about Milwaukee in Game 1, and Boston looked like the team we all thought they would be six months ago, and perhaps we should've seen a lot of it coming.