DETROIT -- Detroit Pistons coach Stan Van Gundy wasn't necessarily surprised to see the Boston Celtics move down in the NBA draft and nab Jayson Tatum with the No. 3 pick in June. "I thought he was the best prospect in the draft. He's got all the tools," Van Gundy declared before Sunday's visit from the Celtics.

But while Van Gundy thought he'd be an excellent pro, he draws the line at anyone who suggests they knew Tatum was going to emerge as a legitimate 3-point threat at the NBA level.

Heck, a graphic displayed during the draft broadcast pinpointed Tatum's biggest weakness as 3-point shooting.

"Anybody who says they're not surprised by his 3-point shooting based on what he did in college is lying," Van Gundy said. "I mean, if there's somebody who said, 'Oh, look, I knew he'd knock down 50 percent of his 3's,' even though he made 32 percent of them from the college line, they're lying. And I'm sure there's somebody saying that, that they knew, but they're lying. But everything else was there -- his ability to put the ball on the floor and get shots. He's got a real poise to him."

The 19-year-old Tatum continued his impossibly accurate long-distance shooting on Sunday night in Detroit, connecting on three of the five triples he attempted. Those makes included a 3-pointer with 1 minute, 55 seconds remaining that essentially secured Boston's 91-81 triumph at Little Caesars Arena.

Now, more than a third of the way through the 2017-18 season, Tatum leads the NBA while shooting 52.3 percent beyond the 3-point arc. He's more than 4 percent ahead of the nearest qualifier (Al-Farouq Aminu, 48.1 percent).

Tatum has connected on 46 of 88 3-pointers overall, and half of those makes have come in the past 10 games while shooting 60.5 percent from beyond the arc.

It's not just the 3-pointers he's hitting, but when they're coming in the game. Tatum's late-game triple on Sunday night in Detroit gave him 39 points during clutch time (game within five points in the final five minutes) and, aided by Boston's high total of clutch games (Tatum has been on the floor for 17 out of Boston's 19 such games), Tatum was tied for 11th overall in the NBA in total clutch points (39) entering Sunday evening's games.

What's more, Tatum is shooting a staggering 66.7 percent in those situations, the highest shooting percentage among any player in the top 25 in total clutch points.

"Some people have it and some people don't. It's just as simple as that," said Kyrie Irving, who is second in clutch points, trailing only former teammate LeBron James. "I think [Tatum has] pretty much shown that he can play, as people say, with the big boys at the end of the game, without wavering in terms of his decision-making or anything like that. He trusts what we have going on and he knows where his opportunities will be, especially down the stretch."

Tatum finished with 11 points on Sunday, one of five Celtics players in double figures in a game that won't be remember for his offensive beauty. Boston led by as much as 18 but the Pistons made a late surge. With the Celtics clinging to a five-point lead with less than two minutes to play, the ball swung to Tatum on the right wing. Kyrie Irving had drawn two defenders cutting towards the basket and Tatum was open as Al Horford fed him from the top of the arc. Tatum calmly splashed the shot even as Andre Drummond rushed out to contest.

"The shot that he hit that was off of a lot of attention on other guys on the other side of the floor," Celtics coach Brad Stevens said. "That's why he was open. He benefits from that and then he's obviously a good player that we think will get a lot better."

Jayson Tatum, currently shooting 52.3 percent from three, is trying to become the first rookie with enough attempts to qualify to make more than half of his three-point attempts. Rick Osentoski/USA TODAY

Tatum makes his 3-pointers look effortless. Teammates and coaches have remarked how it looks like every shot is going in. He rarely misses badly and only a few of his makes seem to even scrape the rim.

Tatum has shrugged off the questions about how he was able to improve so quickly after shooting a mere 34.2 percent beyond the arc in his lone season at Duke. He has noted how he put an emphasis on stretching out his range as he worked out in advance of June's draft. Even though he didn't always shoot with the sort of consistency in his draft workouts that might have suggested he'd at least be a 3-point threat, it was obvious to the Celtics he was a solid enough shooter that he would eventually make those shots.

Jayson Tatum shot areas Jayson Tatum is actually shooting better from 3 (52.3 percent) than he is from the non-restricted area of the paint (28.0 percent) and the mid-range (43.2 percent) so far as a rookie. SHOT AREA FGM FGA FG% Restricted Area 59 99 59.6 In The Paint (Non-RA) 7 25 28.0 Mid-Range 19 44 43.2 Left Corner 3 8 16 50.0 Right Corner 3 9 11 81.8 Above the Break 3 29 61 47.5 Source: NBA.com

At summer league, Tatum dazzled with his Paul Pierce-like midrange game, but Stevens emphasized in the aftermath the benefit of the 3-point shot.

"I think one of our challenges this summer was everybody wanted to talk about the midrange plays he made in summer league. So it was one of those things where if I was involved in a film session at all this summer, it was about what a good shot looks like when you get to the NBA," Stevens said. "And so we tried to have those very specific film sessions but, still, you can't predict a guy is gonna become that proficient.

"He still can play in the midrange. We still want him to take good midrange shots. But we have tried to make it an emphasis to not hesitate to shoot. He's so tall that on the catch he can get that shot off, and his inclination has probably always been to fake it and drive it. But he shoots it with ease and feels good every time he shoots it."

Celtics big man Al Horford, who has stretched his game beyond the 3-point arc in recent years, thinks it showed maturity for Tatum to embrace that change in his own game.

"He likes to play [in the midrange]. To sacrifice for the team in order to give us our best chance to play the right way and win, he had to make some adjustments," Horford said. "And he's done it.

"I think for him it was difficult. But the one thing I've seen with Jayson is he's able to make adjustments and learn. He just keeps learning, he keeps making the right reads. He still has the midrange game, but I think that he's in a point where he feels more comfortable shooting 3s."

Irving has emphatically dismissed the idea that Tatum's leap in 3-point percentage is all that surprising. He points out that the NBA level has put Tatum in better position to shoot those 3-point shots.

"When you're in a different kind of environment you get put into different positions. [Duke] coach [Mike Krzyzewski] utilized him the best he could in their offense last year and I think it was predicated on iso basketball, where he caught it around the elbow and was able to play the 3-4 spot. And then in high school he was just bigger than everybody, so like why would he need to shoot 3s?

"When you're as skilled as he is, and then you're now in a high-intense, high-talented offense, you get a lot of open looks where you can get your feet set. And I think he's doing a great job of realizing that teams are running him off the line but he can still get a great look off penetrating or relocating to the 3-point line."

Van Gundy might take umbrage if Irving were to claim he foresaw Tatum's 3-point leap. No one could have imagined Tatum being this efficient. And that he has maintained it this long is only confirmation that he's got a future as an impact player at this level.