BOSTON — Gordon Hayward chose his words carefully and seemed reluctant to divulge too much information when pressed about the Boston Celtics’ secret weapon this season.

The Celtics have recently started calling it, “The Theis,” and it used to be “The Gortat.” Really, it's just a seal. Think when a big man thrusts his backside into a nearby defender, typically under the guise of positioning for a rebound, but more often to pave a runway to the rim for a driving teammate.

At the start of the year, the Celtics nicknamed the move, “The Gortat," as a nod to the NBA veteran Polish big man Marcin Gortat, who made a living off screens and seals. But Boston has enjoyed so much success with the seal this season that it decided to rebrand their version in honor of third-year big man Daniel Theis.

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For all the whistles he draws in just about every other game situation, Theis has quietly become elite at bending the rules just enough that teammates such as Hayward and newly minted Eastern Conference Player of the Month Jayson Tatum can get some easy layups at the rim.

"I think he’s the best in the league at it,” said Hayward, before quickly turning coy again. "Hopefully we don’t let out all our secrets here because not that many teams are doing it yet. But it’s a really good option and it works for us.”

Given Boston’s collection of drive-happy wings, members of the team’s coaching staff queued up film of Gortat early this year and highlighted the way the former NBA big man pried open driving lanes by putting his body in the right position after his screens. The move quickly caught on but especially with the crafty Theis.

“[Gortat] used to do that in a game and, all the big men, we hated it,” said veteran Enes Kanter. "It’s impossible to block the guy who is coming off the pick, it’s just so hard because the big is sealing you. So we watched a lot of film about it and said, 'We gotta start doing it.’ Me, Theis, and [rookie] Vincent [Poirier], we’ve been doing it. I just think it’s working really well because it’s so hard to block a shot when a big is sealing you and the other guy is going up for a layup.”

It’s hard to quantify seals. They are often just the offspring of an initial screen, which the NBA does track as part of its hustle stats database. Through Wednesday’s game, Theis ranked 10th in the NBA with 535 screen assist points generated through 55 games. His 226 total screen assists ranked 11th overall.

Theis is elite at helping the others in Boston’s talent-filled starting five generate the space necessary to maximize their offensive talents. Why, though, is he so good at the seal?

"He played in Europe, so he’s got that high basketball IQ,” said Kanter.

Added Hayward: "I don’t know. Maybe he learned [the seal] somewhere else or he naturally did it on his own, he just has good timing on it. So knowing kinda how fast to roll, and when he should roll to the rim. And when he should roll for a seal. Also when to pop and things like that. Daniel Theis just has a really good feel for the game.”

HOW "THE GORTAT" BECAME "THE THEIS"

In his rookie season in Boston, Theis said the scouting report warned him what to expect from Gortat. But that couldn’t prepare him for a hands-on tutorial.

“Our scouting report said don’t let him screen you,” said Theis. "I think he [sealed] a little earlier, like when you try to defend the pick-and-roll, he seals it right away.

"We've been calling [Celtics' seals] it all year, 'The Gortat.’ But now it’s ours.”

Well, more specifically, it belongs to Theis. Kanter isn’t exactly sold on the name, noting that, “The Gortat” has some bite to it, whereas, “The Theis,” doesn’t roll off the tongue as easily. Still, he’s all for Theis owning the move.

In fact, when opposing big men try to co-opt the seal from Boston’s playbook, Kanter and the other reserves will call them out on it.

“If we see another team trying to do it, we’ll yell at them from the bench,” said Kanter. “Like, ‘Hey, that’s our move!’”

The Celtics know it’s a copycat league. Opposing coaches have already made note of Theis’ craftiness. Hayward is more worried that, if teams start abusing the seal, then referees might start calling Theis for it in the instances where he’s maybe a bit too quick to initiate contact (though Theis believes he’s more often within the rules).

The last thing Theis needs is more whistles. He’s been whistled for 191 personal fouls this season, tied for the seventh-highest total in the NBA. This despite the fact that Theis plays only 23.5 minutes per game.

Celtics coach Brad Stevens noted that Theis has put in a lot of work to get good at those seals, and credits his basketball IQ and overseas experience for being so skilled at them.

“He works hard on them. We work every day on those seals and Theis is great at the pace of it,” said Stevens. "But he also works really hard at not fouling — that is a huge emphasis."

NOW, ABOUT THOSE REFS...

Every now and then referees will call him on it. Not as much as, say, former Celtics big man Aron Baynes used to get whistled. But enough to keep Theis honest.

"I got whistled in Portland,” said Theis. “The referees told me I gotta show my hands more so I did that in the second half. I think it’s just like, over time, you learn, trying to be a threat as a roller or sealing. Some games it works, some games it doesn’t. It’s a good weapon for us just to get [Tatum] easy layups. It can help get Jayson going, get some easy ones in the beginning.”

Tatum often shows his appreciation for Theis behind the scenes but also publicly spotlighted Theis’ seals on the recent trip out west. Theis initially said he didn’t need the praise but, watching Tatum blossom into a bonafide star thanks, at least in small part to Theis’ efforts, the German big man is playfully reconsidering whether he could use a token of appreciation.

“We watch video sometimes [and players will applaud the seals]. I appreciate it,” said Theis. "I think Gordon [noted it to the media] last week, too. I told Jayson that my birthday is coming up soon. We’re going to see what he’s going to get me for my birthday.”

Tatum, who turned 22 on Tuesday, has plenty of shopping days left. Theis doesn’t turn 28 until April 4. There’s ample time to find just the right gift for a player that’s content to do the dirty work for the benefit of the team’s stars.

Stevens has pointed out how well Theis pairs with Boston’s other starters in Tatum, Hayward, Kemba Walker, and Jaylen Brown. That lineup has still only played 188 total minutes this season but has a glistening net rating of plus-12.5 in that span. That includes a 121.1 offensive rating that is second-best among all lineups with at least that much floor time.

"A LITTLE MOTIVATION"

Center was supposed to be a glaring weakness for Boston after the departures of Al Horford and Baynes. The Celtics signed the 6-foot-10 Kanter for help on the glass but the 6-8 Theis quickly locked up the starting job when Kanter bruised his knee on opening night.

Theis’ efforts are a big reason why Boston owns the fourth-best defensive rating in the league, allowing 106.2 points per 100 possessions. He still has rough patches against heftier bigs but shined the last time Joel Embiid and the Sixers visited Boston. Theis is quick enough to stay in front of some guards and can chase bigs out to the 3-point line.

Theis has been excellent since the All-Star break. It started with a career night in Minnesota (25 points, 16 rebounds) and he’s averaging 13.7 points and 8.7 rebounds over 27.5 minutes per game in the seven games since the break.

Before that Minnesota game, his soon-to-be 4-year-old daughter Laila requested her dad score 100 points against the Wolves. Theis talked her down to 11 points and 11 rebounds then posted a career night.

"Last game, she went up again, she said 35 and 35,” said Theis. "It’s good. A little motivation.”

But Theis' best work still comes with little fanfare. Watch No. 27 in the paint the next time Tatum attacks. Chances are you’ll see a big reason why Tatum has emerged as a legitimate star and why the Celtics are on pace for 57 wins.

For Boston, "The Theis” is right.

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