Daniel Theis has quietly been one of the most consistent players for the Boston Celtics in his second NBA season. While most of the roster has struggled to figure out their roles on the team (Kyrie Irving and Marcus Morris not included), Theis has been nearly the exact same player since his first game in a Celtics uniform. At 6'8", Theis has molded into the ideal stretch-five, combining every quality of a classic rim-running center with the modern opportunistic three-point shooter.

Hidden in plain sight

When I call Theis the secret weapon I don't mean that he might randomly go off for 30 points when you least expect it, or that he's the type of raw talent that we expect to become a cornerstone piece in the coming years. Instead, the best-kept secret is that Theis is a positive contributor to the Celtics as consistently as Morris and Irving are, albeit with no spotlight and no expectation whatsoever. Positive contributions from Theis are nearly guaranteed on a nightly basis, and yet it goes largely unaccounted for in the greater narrative.

While you weren't looking, Theis has swooped into the top five among his teammates in an impressive list of statistical categories. Here's the list (Robert Williams and PJ Dozier's rankings are excluded because they've played a ton of garbage minutes and have absolutely bonkers advanced stats as a direct result):

• 1.9 Box plus/minus - fourth behind Marcus Smart, Al Horford, and Kyrie Irving
• 1.2 Defensive box plus/minus - third behind Marcus Smart and Al Horford
• .188 win shares/48 - second behind Irving
• 3.4 block percentage - second behind Al Horford
• 14.4 total rebounding percentage - second behind Aron Baynes
• .611 true shooting percentage - second behind Marcus Morris (!!!)
• .302 free throw rate - second behind Aron Baynes
• 17.0 PER - third behind Horford, Morris, and Irving
• 124 offensive rating - first on the team

Role players like Theis are just as important to the cohesion of a basketball team as the superstars that headline the show. Take a look at any "overachieving" team -- this year's Los Angeles Clippers, for example -- and you'll find that it's a roster comprised almost entirely of role players. Nobody tries to do too much because there's no expectation set on how much workload any particular player is responsible for. This Clippers team is so high above their floor that nobody knows how high their ceiling should be. The Isaiah Thomas-era Celtics were the perfect example of this, and Daniel Theis is essentially the modern Amir Johnson.

Here's a per-game comparison between both Theis and Johnson's second year with the Celtics: 

And here are the advanced stats: 

Like the backup center before him, Theis is on the Celtics to fill in the gaps. Setting screens, fighting for rebounds, and taking open shots make up the bulk of his role, and he's done a fine job to help keep the Celtics afloat.

Also of note in the statistics department: Theis is assisting on his teammates' field goals on a more consistent rate (10.6%) than Jaylen Brown, Jayson Tatum, and Marcus Morris. Some of Theis' stats are inflated by playing a chunk of his total minutes in garbage time -- and the Celtics have played a lot of garbage time this season -- but Brown has played even more garbage minutes than Theis, while Tatum has played roughly the same amount (per Cleaning the Glass, which subtracts garbage minutes from their data).

Just the tip

Boston has struggled to win battles on the glass this season, although Theis has made some clear strides of improvement as a rebounder. Before we get into it, I'd like to point out that rebounding stats, in general, are pretty dubious for a few reasons:

• Many rebounds go completely uncontested.
• Sometimes players deliberately get out from under a rebound so their teammates can catch it.
• Sometimes this is for stat padding reasons. Sometimes it's so that player can act quickly with the ball in transition.
• Players who box out effectively will occasionally do so in order to clear space for a teammate to swoop in for the ball, which yields no rewards in the box score.

To fill in the gaps left by inconclusive numbers, we have video. Like this one:

Theis clears out after Rozier predictably doesn't look to hit him as a roll man. Off the missed shot, he camps out behind Thaddeus Young, who actually has the better position. Theis not only times his jump better but also has the presence of mind to slap the ball away, instead of trying to grab it over Young's outstretched arm. Little advantages like these are the difference between staying alert and simply going through the motions. While Young was in position at the correct time to grab the board for himself, he never actually boxed Theis out of the area, giving Boston a free possession.

Here's a play the Celtics ran against Minnesota that I thought was particularly cool:

Theis sets a pick for Smart and rolls to the basket. Smart hesitates for a second and then brings the ball up high as if to throw an alley-oop pass for Theis. All five defenders turned their attention to Smart with four of them moving towards the paint to break up the play. This opens up Tatum to shoot the ball from the corner with zero defenders nearby. Tatum misses the shot, but Theis is there to clean up. Again, he camps out behind the defender (Josh Okogie this time) who doesn't box him out aggressively enough to keep him away from the ball. Theis times his jump perfectly and the Celtics get another chance.

I slowed the play down a bit by taking some screenshots and describing them in this tweet.

As we enter the second half of the season, we should keep an eye out for who plays the most relevant minutes as Brad Stevens shores up his rotations for the playoffs. Between Theis, Baynes, Horford, and Williams, there are a lot of minutes up for grabs. I wouldn't call it a logjam at center, given that the only player in the group whose minutes are safe are Horford's. That being said, Horford has been on a minutes restriction for some time now, so we'll get a chance to see what all the big men are made of as the Celtics try to find their groove again.