BOSTON — Daniel Theis isn’t typically regarded as a high-flyer but there are moments this season when he appears shot out of a cannon. Like last week in Miami, when he caught a pass flat-footed in the charge circle and somehow elevated over the springy Bam Adebayo and threw down a loud two-handed slam.

Or earlier in the month when Phoenix’s Mikal Bridges accelerated at the basket and Theis soared high while blocking his layup attempt into the second row beyond the baseline.

“Sometimes [Jayson] Tatum will tell me, ‘I didn’t know you could jump like this,” said Theis.

There’s a lot of things the Celtics might not have known that Theis could do before this season. Whether it’s providing veteran leadership in a young locker room or emerging as a reliable starting center on a team with lofty goals, the 27-year-old has been a steadying presence for a Celtics squad that's dealt with a revolving door of injuries.

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On Saturday night, the Celtics learned that Theis might just be able to hang with All-Star big man Joel Embiid. Theis has struggled against beefier bigs in his career, their size sometimes overwhelming him around the basket. So when Embiid flipped a little baby hook over Theis on the game’s first possession on Saturday, it was fair to wonder if it was going to be a long night for a Celtics team thin on healthy bigs.

Instead, it was Embiid’s only bucket of the night. With help from Marcus Smart’s frequent doubles, the Celtics limited Embiid to 11 points on 1-of-11 shooting overall. The NBA’s matchup data had Theis logging a team-high 6 minutes of matchup time against Embiid and limiting him to 4 points on 1-of-7 shooting with two turnovers and only one shooting foul. That’s encouraging when you consider Embiid had put up 11 points on 4-of-6 shooting versus Theis earlier int the year).

“Our whole team, we made it hard on him,” said Theis. “We tried to make him catch it outside. Every time he tried to spin, somebody was there [to double]. I have to use my speed a little bit, because I can’t body him the whole time.

“But I annoyed him a little bit. That’s what I gotta do. Overall it was a great defensive game for us.”

The Celtics had an impossibly low defensive rating of 79.6 during Theis’ 26 minutes of court time Saturday. For the season, Boston’s defensive rating with Theis on the floor is 102.9, or more than a bucket better than their season average of 105.1, which ranks third in the NBA.

Boston’s defense, you’ll remember, was supposed to fall off a cliff after the departures of Al Horford and Aron Baynes. The Celtics signed the offensive-minded Enes Kanter for backline help this summer but Theis' re-signing flew a bit more under the radar.

Theis has started 43 of Boston’s 48 games this season. He’s averaging a modest 8.1 points and 6.2 rebounds while adding a career-best 1.4 blocks per game. On offense, he’s content to take open looks when they come his way and has emerged as an elite sealer, often paving paths to the basket for Boston’s perimeter talent by simply jamming his posterior into an opposing big man and shuffling backwards. About the only quibble is that Theis’ 3-point shooting has plummeted from 38.8 percent a year ago to a career-worst 30.5 percent this year and he needs to be able to make that shot to keep defenses honest.

But Theis’ versatility, his defensive effort, and selfless nature have been key to Boston’s overall success.

"He’s been great. Really reliable,” said Celtics coach Brad Stevens. "He gives you a good scoring threat, at the rim, and at the seams on rolls, can pop and shoot it a little bit. Then, defensively, he’s great with his ball pressure.

"There’s always going to be some bigs in there that are tough because of the rebounding and post-ups. One of the things that keys our ball pressure is him. He’s out there picking up bigs that teams try to play through in the 5-out look and he’s been putting guys on their heels and that’s been a big part of our team.”

Kanter draws a lot of attention for his offensive rebounding abilities but he’s often made it a point to shout out Theis — sometimes unprompted — because he wants others to take note of what the German big man is bringing to the team.

“He’s like the glue guy that I always talk about,” said Kanter. “He’s one of our leaders. He’ll say, ‘Hey, let’s get this right.’ He’s played here before, he’s well-respected in the league. And he does so much for our team.

“It’s not about the box score. It’s not about 20 points and 10 rebounds, or having this many assists. He does so many things that’s not on the stat sheet. We see it but sometimes the fans don’t. … He’s done an amazing job. Starting is so much pressure, especially with [all the talent around him]. But he’s being an amazing teammate.”

Theis likes to get in his playful jabs during locker room banter but he’s typically pretty quiet. That’s why it’s a bit of a surprise to hear that he can be a bit of a vocal leader on this team.

When the Celtics hit a rough patch in January, teammates said he was one of the players who routinely spoke up hoping to get things back on track.

“I think people forget that I’ve played professionally since I was 17,” said Theis, who reached Germany’s top league — Basketball Bundesliga — in 2010. A three-time German champ, the Celtics signed Theis in the summer of 2017 but he’s really settled in this season.

"i just try to keep our team together,” said Theis. “I’m the 5, I see everything on the court. I try to keep the defense together. … We know that Smart, Kemba [Walker], all those guys are our leaders, trying to keep the team together, but sometimes it’s also important for other guys to step up.”

Theis clearly absorbed a lot playing behind Horford and Baynes the past couple seasons. During a visit last month, Baynes noted, “[Theis is] playing the right way. He’s staying within his game and he's playing well for them. It's good to see.”

Many Celtics fans have spent the season yearning for an upgrade at the big-man position. It’s certainly been fair to wonder, at times, if Theis and Kanter can hold up against the elite bigs of the East, Embiid and Giannis Antetokounmpo in particular.

Saturday’s effort probably won’t calm those cries and much of Philly’s struggles tend to be self-inflicted. But nearing the 50-game mark, it’s clear that Theis positively impacts winning. Teammates have repeatedly noted that he doesn’t get the respect he deserves.

Heck, not even the NBA officials are giving Theis much respect. In what Celtics Twitter has playfully dubbed, “The War on Theis,” Boston’s big man has repeatedly dealt with foul trouble from ticky-tack calls that go against him. Kanter has told Theis he needs to be better at buttering up the officials and trying to charm them a bit in hopes of avoiding those calls.

For his part, Theis said he’s resigned himself to stop complaining as much when calls don’t go his way.

"They’re not going to change the call anyway,” he shrugged.

Theis noted that Baynes used to tell him to stay vertical and keep his hands up where the referees could see them so that they don’t have a reason to whistle him. Theis can often be seen emphatically motioning to keep his hands high. It hasn’t helped. There was one sequence in Miami where Theis got smacked in the face chasing a rebound and the referees called a jump ball and the big man was incredulous.

"Enes comes to me every time and he’ll say, ‘You’re getting no respect,’” said Theis. “Sometimes I’ll talk to the referees and they’ll say like, ‘My bad,’ after they check a call at halftime. But it doesn’t matter because I got the foul anyways.”

Theis is just going to keep doing what he does. He feels healthier further removed from the meniscus injury that cut short his rookie season. He ranks among the best at his position in both block percentage (3.3 percent, 88th percentile) and steal percentage (1.3, 71st percentile), according to stats-tracking site Cleaning the Glass. After ranking in the 3rd percentile in foul percentage the past two seasons, he’s up to 11. Hey, it’s progress.

Maybe eventually he’ll get more respect. From officials, from Celtics fans, from those around the league. But he’s OK with flying under the radar.

Yes, Theis is perfectly content to keep surprising everybody.

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