“Go get the ball, Jayson!”

“Just take him, Tatum!”

“Every time! Just like that!”

I grew up in the Boston Garden. My dad’s season tickets are older than Dave Chappelle and Terrell Owens. I love the Celtics more than anything short of friends and family, but in a way, they ARE family. I read every NBA book ever written and once spent three years writing my own 750-page NBA opus. I have a Google doc of a 110-player NBA Pyramid, spun off from my book, that I update every month just because I am insane. I remember more about the NBA than I do about things that happened in my own life. I watch random old games in August on NBA TV that I’ve already seen for no reason whatsoever, then text my one buddy who loves the NBA as much as me, and usually he’s watching the same game, and neither of us think this is weird. I am comically, stupidly obsessed with the NBA. Of the 50 greatest moments of my life, maybe 16 of them happened at a Celtics game.

(This is not normal. I get it.)

Considering I have watched this particular Celtics team, day in and day out, since October … you would think I had answers … for … well … this.

And I can’t explain it.

I can’t explain the most delightfully unexpected Boston playoff run since the Holy Winter of 2001.

I also can’t explain how this century’s most blessed and fortunate fan base — which extends from Maine to Hawaii, with transplants spread everywhere (including me) — found itself completely blindsided by a potential Finals team.

We haven’t seen a team accomplish what the Celtics are doing since the 1970s, when the NBA was missing foreign players and a 3-point line, when everyone wore flimsy Converses and didn’t know what the word “arthroscopic” meant, when everyone flew commercial and routinely played four games in five nights, when players chose beer and cocaine over Pilates and hyperbaric chambers, when coaches dressed like this …

Back then, the upstart ’76 Suns, precocious ’77 Blazers and young-and-hungry ’78 Sonics made the Finals, and it didn’t make much sense. But it made a LITTLE sense. Why? Their best players were actually playing. They had Westphal and Adams and Walton and Lucas and D.J. and Gus and Sikma and Sikma’s hair. The 2018 Celtics have Kyrie and Hayward … in street clothes. The 2018 Celtics are favored to make the Finals Sunday night, even with the league’s best player in 20 years standing in their way. The 2018 Celtics make no sense.

You can win three football games and steal a Super Bowl. You can steal a college hoops title in two weeks. You can win a Stanley Cup with an expansion team. The NBA doesn’t work that way. The better team always wins a seven-game series unless it veers into the Injuries/Officials/David Stern vortex. (Shout-out to Sacramento!) In this decade, every Finals has featured a future top-30 all-timer on both sides, along with four to five other Hall of Famers sprinkled around like role players in a Scorsese flick. The last four WTF Finals teams were the ’09 Magic, ’07 Cavs, ’86 Rockets and ’81 Rockets, but those teams also had Peak Moses, Hakeem and Ralph, Young LeBron and Peak Dwight. The last two champions missing a superstar were the ’04 Pistons and ’79 Sonics.

As far as I can tell, nobody has ever won four playoff games, much less 11, when they were missing their two best players. But it’s even crazier than that. They won 10 straight home playoff games with Al Horford and 11 teammates who make, collectively, a shade less than LeBron James earned this season. Other than Horford, their two most important players are only a combined four years older than Kyle Korver. And their most reliable scorer, by far, doesn’t always want to shoot. (Hold that thought.)

I would describe them as a masterfully coached group of unafraid, unselfish, high-basketball-IQ athletes who hustle their asses off and cannot be bullied. They close out on 3s and race back on defense as well as anyone. Their Zoltar Machine of a coach always seems like he’s two steps ahead of the other team, and the success of his big-moment plays after timeouts is becoming genuinely creepy. On the pivotal play that decided Game 3’s overtime in Philly, he called a play to peek at their defensive strategy, called a second timeout, then drew up the playground play in which Al Horford sealed off Robert Covington for a lob for the winning basket. Why? Because Covington switched to Horford on the dummy play. Stevens calmly figured this out the same way you might butter an English muffin. That’s every night.

Stevens has become so popular in Boston that, when they announce the starting lineups, the crowd cheers for him like he’s one of the starters. In general, the jovial atmosphere for this playoff run ranks with anything we’ve seen since the Bird era — it’s like Boston finally landed its own Cinderella for March Madness. On my podcast this week, J.J. Redick admitted that it was the loudest crowd he’s ever heard. These Celtics feed off their fans in ways that, frankly, don’t happen in professional sports anymore. The crowd becomes their own personal Black Panther suit. That connection is real. You can see it and feel it.

These are all wonderful things. But they shouldn’t translate to a Finals appearance.

You have to dig deeper. Check out the chips on their shoulders. Al Horford has had his butt cheeks kicked by LeBron for his entire career. Jayson Tatum can’t believe Philly picked someone else. Jaylen Brown will never forget everyone booing on Lottery Night. Terry Rozier waited three years for any semblance of a chance. Aron Baynes is a rough-and-tumble Australian who doesn’t care that he’s the white guy with the man bun who just got dunked on in your Twitter GIF. And the Marcuses (Smart and Morris) define themselves, and every decision they make on a basketball court, by that bulky chip for better and worse.

There’s an irrational confidence with these guys that borders on lunacy. I sat next to my 70-year-old father for three playoff games and never heard him yell, “NO-NO-YES!” more in my entire life. Smart launched a 29-footer on Wednesday night that, if I could have paused the game, grabbed a ladder and pounced on it like a live grenade, I would have. This shot made my dad yelp like he’d accidentally stepped on a rusty nail. Nooooooooooo! What happened? Smart swished it. Of course he did. This is the best “NO-NO-YES!” Celtics team ever, and it’s not close. (Also, they might kill my dad. Stay tuned.)

They can weather devastating plays or sequences in an almost supernatural way. The scoreboard could fall on Semi Ojeleye and this team would wait for them to clean up everything, whisk Semi’s body away, then emerge from the timeout and calmly run a pindown screen for Jaylen for a 3. Twice during these playoffs, an opponent hit a ludicrous, backbreaking shot off a defensive brain fart to force an overtime. Nobody hung their heads, rolled their eyes, pointed fingers, anything. Both times, the Celtics won. And it goes back to a recent quote from Zoltar Stevens.

Mental toughness in general isn’t being the most physical or just being able to make the big shot. It’s being able to do your job on the next play every single time. That’s hard to do. That consistency isn’t for everyone. And that’s why it’s the mark of really good players.

That quote and so many other qualities remind me of the 2001 Patriots: exceptional coaching, do-your-job, on-to-the-next-play, young stars, tough veterans … and a second life after everyone wrote them off. That Patriots team didn’t have a great player, just a bunch of good ones. Brady wasn’t all-caps TOM BRADY yet, but he carried himself like a seasoned pro, came through a few times, seemed unusually calm in big moments. His teammates loved him. He idolized Joe Montana, and once we found that out, everything made a little more sense. “Maybe he could be our Montana,” some of us thought. “Maybe.” We didn’t know for sure.

With Jayson Tatum? We know.

But he doesn’t know.

And that’s the most improbable thing about the most improbable Celtics team ever: Their best player doesn’t know he’s their best player.

(Yet.)

“Go get the ball, Jayson!”

“Take us home, Tatum!”

“All day, Tatum! They can’t stop yoooooou!”

Two of the oldest NBA franchises are the Boston Celtics and the New York Knickerbockers. Neither has really changed since 1946. You can always count on the Knicks to do something dumb, and you can usually count on the Celtics to exploit someone else’s foolishness with an always-evolving combination of savvy and luck. That’s how they landed Bob Cousy, Bill Russell, Sam Jones, John Havlicek, Larry Bird, Robert Parish and Kevin McHale (same trade), Lenny Bias (RIP), Paul Pierce, Kevin Garnett and, most recently, Jaylen Brown, Jayson Tatum AND Kyrie Irving from the Great Brooklyn Heist of 2013.

Red Auerbach would have injected last summer’s Tatum trade right into his veins — they had the no. 1 overall pick and ended up with the prize they wanted, but somehow finagled an additional lottery pick. Even better, they handed him that little extra chip. I didn’t go first? Really? Eleven months later, he’s the most talented Celtics rookie since Bird.

And here’s where I hesitate to keep typing for karma reasons, but fuck it …

Those first two months, we thought he looked like Pierce 2.0. Better shooter, better athlete, superior footwork, taller, longer, and a more polished scorer. (By the way, Rookie Tatum is nearly two years younger than Rookie Pierce.) I attended the first three years of Pierce home games; he couldn’t score as easily as Tatum, and he lacked anything as deadly as Tatum’s Doctor J move (a swooping, freak-armed righty layup that works on either side of the rim). Tatum’s reluctance to shoot remains his most frustrating quirk. For most of Game 6 in Cleveland, like so many other nights before the All-Star break, the rookie seemed happy hanging in the corner and watching everyone else. Even during his better performances (and Friday wasn’t one of them), whenever the ball swung to him, he’d almost reluctantly do something awesome. Did Stevens want him to take it carefully? Were they pacing him?

In December, Tatum injured his finger and crashed into the Rookie Wall like Super Dave Osborne. We all calmed down a little. (Just a little.) Nearly three months later, Kyrie went down … and Tatum started putting it together, right around his 20th birthday.

(Again: He’s 20. Only seven years older than my daughter, who forgets her water for soccer practice 37 percent of the time. Twenty years old? My God.)

Those flashes of brilliance didn’t last for plays, but for best-player-on-the-floor quarters. He made clutch shots, drew crucial fouls, honed his increasingly good sense of the moment. He started comprehending the value of, you know, having your best remaining scorer get more involved in the offense. Everything on the defensive side clicked, especially switching (not easy) and not getting demolished by bigger guys in the low post (save for LeBron, who demolishes everybody). I started getting texts from people in and around the league like “Tatum — WOW” and “Congrats on Tatum, he’s special.” Stories started circulating about Tatum lighting up Celtics scrimmages, about veterans like Marcus Morris and Greg Monroe raving to people around the team that Tatum was, well, different.

We’ve been here before in my lifetime — with McHale, with Reggie Lewis, with Pierce, with Rajon Rondo, even with Jaylen Brown — when you’re watching the same team day in and day out, and suddenly, something magical starts happening and everyone glances around and goes, “Wait, are you seeing this? It’s not just me, right?” That’s been Tatum for two solid months. I could show you the numbers and the advanced metrics, but it’s not about numbers. I could rattle off cool stats like “he’s the fifth rookie ever to play 600 minutes in the playoffs (and the youngest)” and “he’s only the eighth 20-and-under player to average 18 points per playoff game,” or I could explain why Magic, Kobe, Tony Parker, Kawhi Leonard and … (wait for it) … Jaylen Brown were the only other 21-and-under playoff perimeter guys who carried a two-way burden quite like this. (And Tatum is younger than all of them were/are.)

But it’s not about prove-it-to-you stuff. It’s about the quality of his shots. Jayson Tatum can reach any spot he wants. He can beat pretty much anyone off the dribble with either hand. When he misses, it’s almost always his fault and rarely because someone stopped him. (This is the biggest reason why 18 points per playoff game should balloon into 27 to 29 within a couple of springs.) He can dunk over anyone. He can finish twisting layups, drain 20-foot fallaways, bomb 25-footers with a hand in his face. He can stop on a dime and release 15-footers at unblockable angles. He can careen into traffic and draw fouls. He has the Doctor J move. He has a Eurostep already. If there’s three seconds or less on an out-of-bounds play, Tatum becomes the first option, always, because Stevens knows he can get any shot off.

He’s the most polished 20-and-under scorer since Kevin Durant, someone I compared to “Plastic Man crossed with George Gervin crossed with T-Mac” before the 2007 draft. I would have bet my life that K.D., barring injury, was going to be an impact franchise player. I would do the same for Tatum. Why? HE HAS EVERY SINGLE SHOT ALREADY. (Wait, I have to go all-caps a second time.) AND THIS IS THE WORST HE’S EVER GOING TO BE. (Hold on, one more time.) AND HE’S GOING TO BE 20 POUNDS STRONGER IN FIVE YEARS, WHICH WILL OPEN UP HIS ENTIRE LOW-POST GAME. (Last time, I promise.) AND HE DOESN’T REALLY HAVE ANY FUCKING IDEA WHAT HE’S DOING YET.

Here’s a great way to measure someone during a playoff game: Watch how their opponent reacts every time they have the basketball. Are they pointing? Are they rushing around? Are they doubling? Are they giving up things they’d rather not give up just to handle that situation? With Kyrie gone, Tatum is the only Celtic who generates real panic. Cleveland has been praying, for this entire series, that Tatum doesn’t suddenly realize that (a) no Cavalier can consistently guard him and (b) J.R. Smith 100 percent definitely can’t guard him.

When we talk about the 2018 Celtics not making sense, we’re really saying that you shouldn’t succeed past a certain point without that one special scorer/creator, that one freelancer who can save a bad possession, trade crunch-time punches with the other team’s best player, draw double-teams, and occasionally make those back-breaking shots that spoil 20 to 22 seconds of great defense. And that’s true. Kyrie was that guy for Boston. He’s gone. That’s why this doesn’t make sense.

But Tatum …

He’s eventually going to be that guy. And then some. He’s going to be an MVP candidate and a 30-point scorer someday. Maybe sooner than we think. His ceiling isn’t Paul Pierce 2.0; it’s actually … (gulp) … somewhere between Carmelo Anthony and Durant.

For now? He can pull off a decent impression of a lead guy — not for four quarters, but for chunks of games. He complements Jaylen in an unusually perfect way — his talented running mate, a decent heat check scorer in his own right (you saw it on Friday), and someone with a real chance to be a rich man’s Paul George — because every NBA team prioritizes perimeter athletes who can score and defend over basically anything else, only the Celtics already found two of the juiciest prizes. The likelihood of Tatum becoming a crunch-time assassin weapon on a perennial contender pushes that combination over the top. Even now, he elicits ongoing fear from opponents, justified or not, that he’s that guy even if he’s hanging out in the corner for five straight possessions as people scream “Come get the ball, Jayson!” at him.

We all see it. That’s the biggest difference from Round 1 to Round 3 that I’ve noticed. On Wednesday night, fans were screaming at Tatum to take over. They pleaded with him, cajoled him, begged him. Sometimes, he’d listen and we’d end up with Reluctant Hero-ball. He finished with 15 shots and eight free throws. We wanted those numbers to be 25 and 13. His coach kept yelling at him to get the ball. His big brother (Horford) and crazy uncle (Morris) kept yelling at him to get the damned ball. He’s turned us into a bunch of AAU moms. Before the game, a friend with the Celtics told me, “You’re getting your wish tonight” (meaning, more Tatum shots), and at halftime, the same person told me, “He’s supposed to be shooting more!” Somehow, Tatum turned into my third kid. I want my daughter to become more selfish in soccer, I want my son to read more books, and I want Tatum to shoot more.

We can tackle Boston’s future another time: Jaylen’s increasingly staggering ceiling, Horford as the classic old-school Celtic, Kyrie and Hayward, Smart and Rozier, the Kings pick, the Grizzlies pick … it’s an insane collection of assets. But it’s never smart to discuss 10 years ahead with NBA teams, much less five, because you never know. Shaq and Penny, Kobe and Shaq, Payton and Kemp, T-Mac and Hill, the Durant-Westbrook-Harden trip … it’s one of the only constants in NBA history, the graveyard of What If? Teams. We will never run out of them. What if Kyrie and/or Hayward never stay healthy? What if Smart leaves? What if Jaylen wants his own team someday? What if another dumb injury happens? You never know. You NEVER know.

(That was my obligatory karma-obeying disclaimer.)

But of all the rookies with a chance to be special — whether we’re going more recently (Giannis, Davis, Durant, Simmons, etc.), a little further back (Duncan, McGrady, Hill, Webber, etc.) or way way back (Bird, Magic, Jordan, Isiah, etc.) — it’s hard to remember anyone waltzing into a better situation. Other than Duncan, Magic, Bird, and Darko (just kidding), no other special rookie immediately joined a Finals contender. There’s also an alternate universe for this Celtics season in which Hayward and Kyrie never get hurt, then Tatum plays 20 minutes a game and sits for entire fourth quarters. He’s getting both breaks in the same season.

And if you read anything about his life, like this Boston Globe feature, you learn pretty quickly that he spent his whole life preparing for this. It’s the typical “basketball was his only way out/carried a basketball everywhere” stuff, only with some unexpected wrinkles. The previous best player ever from St. Louis was LeBron’s old teammate Larry Hughes … Tatum’s godfather? He took a photo with LeBron when he was 8? He tweeted that picture at LeBron for a return follow when he was 14? He reminded everyone of Paul Pierce in college, then landed on Pierce’s old team?

Tatum arrived in the NBA at the best possible time, a child of the LeBron generation, weaned on stars who work their asses off, never stop improving their games, think like businessmen and cultivate their public personae in increasingly thoughtful ways. His postgame interviews are already incredibly polished and incredibly boring. Like Durant 10 years before him, he just comes off like a rookie who wants to ball and that’s it. Keep getting better. Keep plugging away. The rest will come later.

The best thing about basketball: When you strike oil with a blue-chipper, that dude might stay in your life for YEARS. Bird showed up in Boston when I was 9, right after my parents got divorced, and retired two months after I graduated college. They drafted Pierce just a week before I started dating my wife in Boston; when they traded him exactly 15 years later, I was running my own website, living in Los Angeles and announcing the draft on ESPN. Time flies, people die, kids grow up, stars come and go. And every so often, someone like Tatum shows up — someone with a chance to be great. And you get to watch him every night. What’s better than that?

We hear this thrown around all the time in sports, but Tatum really is the right star in the right place at the right time. He’s getting playoff reps, in all types of situations, that simply cannot be quantified. It’s like banging out an MBA and a law degree at the same time. And yeah, he’s gotten better every round, but the stakes are higher now. Jayson Tatum can dethrone his idol and make the Finals. Tonight. As a rookie. Go get the ball, Jayson.