What the Boston Celtics are doing is virtually unprecedented for several reasons. None are more significant or impressive than Jayson Tatum’s fairytale ascendence towards a ceiling we can't yet see.

Currently facing stiffer defensive coverages, a schedule that features zero lottery teams, without any crutch provided by Kyrie Irving—a shot-taking maestro who was genetically engineered to dissect postseason defenses—the 20-year-old (Did you know Tatum is 20? It’s true!) is by far the most astonishing explanation for Boston being on the verge of the most improbable Finals appearance in NBA history.

Tatum has scored a team-high 312 points in the playoffs, which is 28 more than his co-pilot Jaylen Brown. Boston’s net rating with him on the floor is 17.0 points per 100 possessions better than when he’s not, which is another team high. Against the NBA's third-best defense in Round Two, Tatum averaged 23.6 points and made 52.6 percent of his shots, and the Celtics outscored the Philadelphia 76ers by 32 points when he was in the game. In a critical Game 5 of the Eastern Conference Finals, he finished with 24 points, seven rebounds, four assists, four steals, and two blocks.

Before we dive into what this means for the present and future, let’s quickly zoom out for a couple historical comparisons just because they are all so freaking scary. Only four other rookies have ever logged more than 600 minutes in the postseason: Magic Johnson, Manu Ginobili, Jack Sikma, and Alvan Adams.

Adams, Elgin Baylor, and Kareem Abdul-Jabbar are the only rookies who’ve scored more points in a playoff run than Tatum has, and if Boston makes the Finals there’s a good chance he passes each of them to become the league’s all-time leader. All of this is very nuts. It's a first impression on the sport's biggest platform that dwarfs what some of his most popular preseason comps, like Jimmy Butler and Paul George, did when they were rookies. Just look how Tatum stacks up against young Kawhi Leonard. This is what the maturation of an untradable player looks like.

Tatum has fallen below 11 points twice in 17 playoff games and is Boston's go-to option in the clutch, on straightforward actions that essentially say "here's the ball, please score." If anyone reading this is still unimpressed, Tatum has attempted more fourth-quarter free throws (27) than everyone in the playoffs except LeBron James and James Harden.

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It hasn't all been easy, of course. Compared to the regular season, the percentage of Tatum’s baskets that are unassisted has gone up 17.4 percent (and 15.2 percent relative to his regular-season minutes without Irving). He’s isolating twice as often, per Synergy Sports, and the percentage of his shots that are catch-and-shoot threes has dropped from 23.5 to 12.0. Everything is brand new and lot harder than it was two months ago.

As Tatum cannonballs his way into what may very well be a historically-relevant career, what's most paralyzing is how simple it is to identify the areas in which he can further refine a skill-set most eight-year vets wish they had—from tracking shooters around screens to fighting for position in the post (where, according to Synergy Sports, he ranks in the 100th percentile as a scorer in these playoffs) to streamlining his shot selection. A quick glance at the numbers shows how frequently he leans on mid-range attempts. During the regular season, he ranked in the 90th percentile among forwards on shots between 14 feet and the three-point line, with the game's least efficient look accounting for 22 percent of his field goal attempts.

Some of this is because he's unguardable in space, but he'll be even more deadly once a few of those shots migrate into the paint and behind the arc. The mid-range advantage is a critical tool, but Tatum still needs to learn that he shouldn't access it unless he has to. Growth as a playmaker will likely prove essential.

Tatum's defensive mistakes—he leaves his feet too often on closeouts and tends to go under on pick-and-rolls when he shouldn't—are more harmful on this stage, too. And he often takes off for the rim 5 percent faster than he should, which is one reason why he's below average in the restricted area. But Tatum's True Shooting also still ranks above Chris Paul and Harden. He's learning on the fly and so often exudes the confidence of a star who's as comfortable on the court as he is nestled into a worn spot on his living room couch.

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Incremental annual improvement makes contextualizing Tatum's contributions to this particular team harder than they should be. How can you appreciate what's before your eyes when there's a near certainty that same thing will be 40 percent better in three years? His inexperience is meant to tamp down actual production, but in ways 20-year-old’s before him have merely tantalized, Tatum often looks like any other fully-formed All-Star methodically working his way through complex responsibilities.

The effortless moments take your breath away. He already has a move for every type of defender, whether a big or guard switches onto him. Tatum creates separation in his sleep, with side-step threes (to his right or left!), subtle use of his off arm to destabilize defenders who get too close, and a buffet of hesitation dribbles, crossovers, in-and-outs, and step backs to keep whoever's guarding him on their heels. There is zero need for a caveat when describing how advanced Tatum's footwork is. It's not exceptional for a rookie. It's just exceptional.

And when he doesn't have the ball, veteran defenders deny and crowd him like he's Klay Thompson. Serious respect is given.

Any rookie season that’s worth writing home about is processed through the same lens you might take in an intriguing movie trailer. It sticks in your head and makes you curious about what the finished product will eventually look like. Tatum, instead, glows as a feature-length film garnering rave reviews. His first go around creates minute-by-minute allure but it's so much more than buzz, almost like he’s fulfilling his potential in real time.