When bringing up the best defensive anchors on the league, no legit discussion can be had without the brilliance of Al Horford, yet he's left out as if he's not on the same tier as the best of the best. Al's impact was that of an all-star, yet he wasn't even close to considered for the all-star game and he wasn't considered for all-NBA defensive teams either (that last one drives me nuts). Since I'm broke, I don't have synergysports stats or subscribed to have any in-game footage I want on hand, I'll try my best with the information I have at my disposal to show you that Al Horford is indeed an all-star level player.
Elite rim protection, -8.2 whenever he's contesting a shot at the rim (91st precentile) according to craftedNBA. (https://craftednba.com/players/al-horford)
Always boxes out, his rebound per game stats aren't that high due to him prioritizing box outs. (I'm so sad no nerd decided to have a collection of Al Horford box out videos on youtube, just him flinching...)
Communication anchors any defense he's in, no different in Boston. Rotations are crisp and his help defense is some of the best in the NBA. (I'm so sad no nerd decided to have a collection of Al Horford defensive communication videos on youtube)
Switchable, can defend perimeter players with some success: (Youtube video on Al Horford defense! Lots of post defense, but includes him going out to the perimeter defensively, https://m.youtube.com/watch?v=qL4h5N6I3_A)
One of the best post defenders in the NBA, it wasn't just me who remembers saying Al was Embiid's dad, right? Incase you don't remember: https://m.youtube.com/watch?v=CyRXERv4Drk
Al is disciplined, agile, and communicates well with a incredible feel for defending the pick-N-roll. His ability to combine post defense, pick-N-roll defense, agility and communication enables Robert Williams like no other bigman could in the NBA, elevating Boston from just a great defense to being placed in all-time rankings. (Also there are some clips of his pick and roll defense https://m.youtube.com/watch?v=qL4h5N6I3_A)
Fouls? Those are for rookies! Al Horford averages less than two fouls a game despite his activity defensively putting him in so many situations where that could occur. With Al, defense is an art form since his days even in Atlanta and that hasn't changed one bit. (https://www.basketball-reference.com/players/h/horfoal01.html)
Advanced stats: In D RAPTOR, Al ranks #10. In D LEBRON, Al ranks #2 only behind Rudy Gobert. For D Box +- via basketball reference, Al ranks #5 for all qualified players. Needless to say, his advanced stats are great defensively. (https://projects.fivethirtyeight.com/nba-player-ratings/, https://www.bball-index.com/2021-22-lebron-data/, https://www.basketball-reference.com/leagues/NBA_2022_advanced.html)
The glue to the Boston offense as his intellegent passing, adequate shooting, fantastic feel for screen setting, ability to attack closeouts and is being able to score in the paint when needed was the Al Horford experience on offense, a no mistakes player. For some extra advanced stats, the Celtics were +1.0 (per 100) better in the regular season and +4.7 (per 100) better in the playoffs on offense alone. Oh, and his defense, -2.3 (per 100) in the regular season and -0.3 (per 100) in the playoffs for a historically great defense. (https://www.basketball-reference.com/players/h/horfoal01/on-off/2022)
Overall advanced stats: RAPTOR, he ranks 16th (tied with FVV and J. Allen), Box +-, ranks 18th (tied with D-Mitch), CraftedNBA +- (26th, tied with KP). If an all-star level player is suppose to be around top 30, Al keeps popping up, footage backs up his incredible impact, why should he not be considered an all-star caliber player? (https://projects.fivethirtyeight.com/nba-player-ratings/, https://craftednba.com/player-traits/king, https://www.basketball-reference.com/leagues/NBA_2022_advanced.html)
You have a top tier defensive player in the NBA who significantly improves a offense for a team that just made the finals, a player that has no reason to left out of all-NBA defense teams when Robert Williams made it (yes, I'm saying Al is the better defender, also throw in Marcus Smart while I'm at it). In conversations about the best bigs in the NBA, Al Horford has to be brought up.