Jayson Tatum makes his Celtics teammates better — he has cracked the code for true superstardom

Jayson Tatum (right) and Marcus Smart take the high route after a job well done.Jim Davis/Globe Staff

Should this Celtics team fulfill all of its attainable possibilities, what Grant Williams accomplished Sunday will be celebrated forever.

Maybe, like Scott Wedman’s 11-of-11 shooting performance in Game 1 of the 1985 NBA Finals or Kelly Olynyk’s 26-point gem in the seventh game of the 2017 conference semifinals, it will be anyway.

Williams knocked down 7 of 18 — 18! — 3-point attempts, scored a career-high 27 points, and played the leading role as the Celtics dethroned the defending NBA champion Milwaukee Bucks with a 109-81 rout in Game 7 of the Eastern Conference semifinals.

But let’s not forget why it was possible: Because Jayson Tatum’s poise, playmaking, and mere presence allow his teammates to thrive.

Oh, you had better believe it now: Tatum has cracked the code for true NBA superstardom.

It has been well-documented how the progress Tatum made in enhancing the players orbiting around him was crucial to the Celtics’ turnaround halfway through this season. Sunday afternoon, that progress was confirmed beyond a doubt amid the tensest of circumstances.

It could have been so tempting for Tatum to look for his own offense at the expense of others early in Game 7. He was, after all, coming off a jump-on-my-back-boys 46-point tour de force in Game 6 in Milwaukee, and he was on in the first quarter, hitting all three of his 3-point attempts, while many of his teammates were chilly.

Tatum, who didn’t take his first shot (a swished three) until halfway through the first quarter, and Jaylen Brown combined to shoot 5 for 10 in the first frame; the rest of their teammates were 2 for 14, with Williams and Payton Pritchard threes being the only other buckets. The Celtics trailed, 26-20, and they were fortunate to be that close.

Jayson Tatum rises up for a jumper over Giannis Antetokounmpo in the second half of Sunday's Game 7 showdown.Jim Davis/Globe Staff

The Bucks weren’t just banking on the Celtics’ secondary players missing shots. They were banking on Tatum losing faith in them. Yet there was never a hint of such a thing happening. On one sequence early in the second quarter, Tatum appeared to be taking on Giannis Antetokounmpo one on one, only to find Williams, who drove for an open layup, an easy 2 points that seemed to boost his confidence.

Williams was the greatest beneficiary of Tatum’s disciplined play. The Bucks swarmed Tatum, packed the paint, and dared the Celtics’ perimeter players — particularly Williams, whose looks were almost always wide open — to beat them. And that’s what Williams did, after his slow start. (He made 2 of his first 7 3-point attempts.)

Williams wasn’t the only Celtics role player to take a spin in the spotlight. Pritchard, deployed expertly by coach Ime Udoka and his staff as another scoring threat on a night when Marcus Smart and Derrick White combined to make 3 of 19 attempts, chipped in with 14 points in 17 minutes on 5-of-7 shooting.

Payton Pritchard connects for three of his 14 points Sunday against the Bucks.Jim Davis/Globe Staff

Tatum might have been at his best early in the third quarter, when the Celtics started to wobble the champs. He hit an early three, drove and kicked to Brown (19 points) for a three that boosted the lead to 59-47, and then after a Bucks timeout, found Brown again on a nifty lob for one of his eight assists.

There was one anxious stretch when Tatum picked up his fourth foul with 7:38 left in the third quarter. But the Celtics held strong while he sat out the rest of the quarter, outscoring the Bucks, 13-11, in his absence.

Tatum returned in the fourth to officially and efficiently end the Bucks’ reign, the Celtics systematically pulling away from a gassed opponent. . He finished with 23 points on 7-of-14 shooting, hit 5 of 9 3-pointers, grabbed 6 rebounds to go with the aforementioned 8 assists, and — oh yeah, this is probably what Udoka would want mentioned first — played an integral part in holding the Bucks to 81 points on 36.7 percent shooting.

If this feels like more than your standard second-round playoff series win, that’s because it is. The Celtics took down the defending champs — a tough, admirable team — and they did it largely because Tatum outplayed two-time Most Valuable Player and ridiculous-force-of-nature Antetokounmpo (25 points, 20 rebounds, 9 assists, but zero effectiveness in the second half) when the stakes were highest.

The Celtics now take on the top-seeded Heat in the East finals, and Miami should not be underestimated. But it also must be said: Of their four trips to the conference finals since 2017, this is by far the Celtics’ best chance to advance to the Finals and collect that 18th banner.

They have the talent to do it. They have the resolve. And if Tatum — dispatcher of Kevin Durant in the first round, dismisser of Giannis now — is going to keep playing like this, they have the most complete player remaining in the playoffs.

Funny how it’s all played out. The Celtics, so far away now from that miserable first half of the season, have a very real chance to be champions. And perhaps the biggest reason is that Jayson Tatum became a true Celtics hero when he stopped trying to be one all the time.