Al Horford is the x-factor against the Bucks

The Celtics played the Bucks three times this regular season. They won by four at home, lost by 13 at home, and lost by one on the road. One of these things is not like the others. Of course, there was an explanation for the one outlier result: Al Horford.

In the two close games, Horford starred, averaging 19.5 points, 11 rebounds, 6.5 assists, and 3 blocks. In the blowout, Horford didn’t play at all and neither did Aron Baynes or Marcus Morris, meaning Semi Ojeleye started and Daniel Theis, Robert Williams, and Guerschon Yabusele combined to play over 36 minutes off the bench.

Horford’s monstrous production was causal in the Celtics’ competitiveness with him and lack thereof without the star big man. With Horford on-court against the Bucks this year, the Celtics outscored Milwaukee by 16.8 points per 100 possessions. With Horford off, the Celtics were bludgeoned by 19.9 points per 100 possessions.

The most discussed aspect of Horford’s value vs. Milwaukee is probably his individual defense on Bucks megastar, Giannis Antetokounmpo:

Horford certainly does a good job—or as good a job as one could—defending Giannis. He moves his feet well enough. He is, of course, intimidatingly intelligent and well-prepared. Against the Pacers, Horford brutalized Domantas Sabonis through preparation. He knew to sit on Sabonis’ right shoulder/left hand. Antetokounmpo is not Sabonis, but understanding his tendencies, knowing that he’s going left and spinning right every time is key to providing slightly more resistance than the likely MVP is accustomed to. Every player has things they like to do and Horford is a master at taking them away.

With all that said, Horford’s one-on-one defense on Giannis is probably overstated. Not just in the sense that a “Giannis stopper” is not a thing, but in that the Celtics didn’t put Horford on Giannis as much as you might think this year. The NBA’s match up data is admittedly wonky, but in the first Bucks-Celtics game of the season, Horford defended Giannis for just four possessions, according to Second Spectrum. In the final meeting of the regular season, the only other one Horford played, he did match up with Giannis for 37 possessions, but given the amount of switching the Celtics did in that game, I’m guessing that number overstates the true number of possessions Horford defended Antetokounmpo.

Defensively, Horford’s value against the Bucks seems to stem more from his versatility and intelligence than his stopper equity:

The Celtics do not fear the repercussions of switching their center on to one of the better slashing point guards in the league. Horford, aware of Bledsoe’s lack of shooting, actually turns this mismatch into an advantage, helping way off Bledsoe in the corner and making himself available to help on the Middleton drive.

Horford imprints himself on the game defensively through intelligent help defense on nearly every possession. He knows when he can take certain liberties, and leverages that freedom to gum up whatever it is Milwaukee’s doing. In this specific matchup, though, it’s probably on offense where Horford is most impactful.

Milwaukee’s defensive philosophy is best described as “no paint.” They are absolutely intent on keeping the offense out of the paint, surrendering jump shots instead. They try to funnel these jump shots to the least proficient shooters on the opposing team. Against most teams, that means Brook Lopez sliding down to shut down a point guard’s drive in favor of him kicking it out is a worthwhile trade-off. Most teams don’t employ Al Horford.

In two games against Milwaukee, Horford attempted 17 3s, which was tied for his most against any opponent this year (he took 17 against Toronto in four games). Eleven of those attempts came in the first meeting of the season, in which Milwaukee’s scheme did not adequately account for Horford’s shooting prowess:

For most of that game, the Bucks had Lopez in a deeeeeeep drop when defending pick-and-rolls. When Kyrie Irving comes around the screen at the 3-point line, Lopez sinks a few feet into the paint. Again, most teams don’t employ career 36.8 percent 3-point shooting centers, so this strategy is a much more viable option—it takes away the paint, usually baiting the ball-handler into inefficient mid-range jumpers. The Celtics, however, did not need Milwaukee’s active encouragement to eat in the Irving-Horford pick-and-pop:

Irving’s pull as a scorer is so powerful that he can drag an entire pick-and-roll defense halfway across the court to open his star big man for a great look. Of course, Horford then has the ball-handling and passing to take further advantage of that and secure a catch-and-shoot look for Irving. By the third Bucks-Celtics meeting, Milwaukee had clearly learned its lesson and moved away from the deep drop against Horford:

Nonetheless, the Celtics generated good looks out of the Horford pick-and-pop, though not quite at the same volume as the first meeting of the season. And while the drop is not as aggressive as it was in the first game, the Bucks were still deploying drop coverage, which the Celtics found clever ways to exploit and unleash Horford’s shooting:

This is like a Spain pick-and-roll, in which the ball screener’s man is screened by a third player, but a pick-and-pop version designed to make use of Horford’s exceptional shooting. The shot doesn’t fall, but it’s as open a look from 3 as you’ll see in an NBA game.

On offense, Horford is the furthest thing from one-dimensional:

When Irving finds his way into the paint, he draws help and creates an advantage opportunity for Horford, he is not simply going to shoot. He’s going to evaluate the floor, calmly and quickly, and without fail, he will make the right decision, creating an even better scoring opportunity. And sometimes, he creates the entire scoring opportunity himself:

Sending a post double at Horford is death. He will find the open man every single time. Horford’s infallible decision-making is especially valuable against a team as aggressive defensively as Milwaukee. They’re so set on taking away the paint that they create significant openings. Lesser players get overwhelmed and fail to see those openings—Horford is not those players.

For his entire career, Horford’s physical tools have been an essential piece in the puzzle of his quiet dominance. He moves with a fluidity that simply isn’t fair for a man his size. He owns a significantly plus wingspan, which he flails about to create havoc on each and every defensive possession.

Against the Bucks, those physical tools have been and will be as important as ever. They’re essential to sticking—again, relatively speaking—with Giannis, enable switching most teams cannot rival, invaluable to Horford imposing himself around the rim as a help defender.

As it has for 12 years now, Horford’s mind will be his greatest asset in this series, though. Defensively, he will take calculated risks and gambles designed to slow the Freak himself, but also to disjoint Milwaukee’s entire approach. On offense, his smooth stroke will be essential, but it’s his ability to leverage the threat of that stroke into advantage situations for his teammates in which he’ll use his unrivaled intelligence to systematically and ruthlessly pick apart Milwaukee’s aggressive defense that will swing the series.

In the regular season, the Celtics were completely outmatched by the Bucks when Al Horford was off the court. That should hold in the playoffs. But with Horford healthy, he gives the team a chance to dominate the way it did with him on the court in the regular season, and replicating that success will likely be Boston’s only path to upsetting the Bucks.