Celtics-Thunder Notebook: Jaylen Brown returns, Jayson Tatum shares injury update, and ‘spacing’ is the word of the day

The Celtics fell to the Thunder in the third of a four-game road trip — here’s what you need to know from on-the-ground in Oklahoma City.

OKLAHOMA CITY — On a frosty cold day in Oklahoma, the Thunder showcased why they’re the best defense in the league — and one of the top teams in the NBA — holding the Celtics to just 27 second-half points en route to a resounding 105-92 victory. It’s the least amount of points the Celtics have scored in a half since 2012, and even Kristaps Porzingis was startled to learn how few points the Celtics’ offense produced.

With the loss, the Celtics drop to 2-1 on their four-game West Coast road trip, and 26-10 on the season. They’ll close out the tour against Denver on Tuesday.

Here are four observations from on the ground in Oklahoma City:

Jaylen Brown returns from a two-game absence; Celtics whole team available

For the first time in 17 games, the Celtics’ entire top-8 was healthy and available to play. Jaylen Brown elaborated on the shoulder strain suffered on New Year’s Eve against the Raptors that kept him out of the first two games of the road trip. Brown said that since Tuesday, he’s been going through his treatment in hopes of returning as soon as possible.

“It was on a play where I was trying to fire it out — my arm kind of got jammed,” Brown said. “I went and got an MRI, came back, and it was a shoulder strain.”

Brown was icing his shoulder post-game in the locker room, and said that he felt physically good in the game. He scored 21 points in the first half on 8-11 FG, but was held scoreless in the second half. He said he was going through his treatment and was eager to be on the floor.

“Felt good today, a little sticky,” Brown said. “But, felt good — this week, was just going through my progressions. I definitely wanted to be available for tonight.”

Thunder head coach Mark Daigneault credited Lu Dort for taking on the Brown assignment in the second half, and Mazzulla noted that played a role in slowing him down.

But, Brown pointed out that Dort was also guarding him for stretches of the first, too.

“I feel like he was guarding me in the first half as well — I just think they switch a lot. I just think our spacing wasn’t great in the second half,” he said.

The Thunder might have the best crowd in the league

Most road NBA arenas are inundated with Celtics fans, and it sometimes feels like the crowd cheers louder when Boston scores than when the home team does.

But not Paycom Center.

From the jump, the atmosphere in the Thunder’s home arena was incredibly lively — and the crowd never wavered despite OKC falling behind by as many as 13 points in the first. There were a few hundred Celtics fans in the arena, as there always are, but they were pretty imperceptible.

By the time the Thunder pulled away in the fourth quarter, the home arena was as loud and celebratory as any road arena I’ve ever been in — including all of last year’s playoff games.

Downtown Oklahoma City was a ghost town on Sunday morning, with temperatures as low as 12 degrees Celsius (and feeling as cold as -5 degrees, given the 40 miles per hour winds). Most restaurants and stores were closed, and OKC seemed like a ghost town.

But, being inside Paycom Center, you’d never guess how desolate the outside was — you would have imagined you were in Times Square.

And, once the crowd got going in the fourth, all of the momentum was on the Thunder’s side. On a glacial Sunday morning, there was no better place to be in Oklahoma City.

Spacing, spacing, spacing, spacing

When Joe Mazzulla was asked to diagnose the Celtics’ second-half woes, he repeatedly referenced the team’s poor spacing.

The offensive stats in the second half were abysmal. The Celtics shot 20% from the field — and a striking 12.5% from three en route to a 27-point second half.

Jayson Tatum scored 15 points on 4-11 shooting, but the rest of the team combined for just 12 points on 4-29 shooting. Jrue Holiday, Jaylen Brown, Derrick White, Payton Pritchard, and Sam Hauser combined for 0-19 shooting. The Celtics finished the half with more turnovers (10) than field goals (8).

“That’s a product of poor spacing, poor physicality on the ball, and poor screening,” Mazzulla said. “Those 17 points off turnovers was a difference-maker. Just multiple, multiple empty possessions with poor spacing. You’ve got to fight for better spacing in those situations against a good defensive team.”

When Kristaps Porzingis was asked about the team, he also brought up spacing.

“Honestly, some stuff we forced a bit — didn’t really give each other enough space,” Porzingis said. “Some stuff they legitimately just played good defense, and some we missed. That’s like a mix of everything. But, I would say we didn’t play up to our level at all offensively in the second half.”

So did Jaylen Brown — multiple times throughout his 5-minute locker room availability.

“In the second half, they upped their level of physicality,” Brown said. “And I think our offensive execution and our spacing let us down in the second half.”

“We didn’t get into our spacing fast enough, and that had an effect on the game. In those moments, we have to be more poised, and I got to do a better of job of getting into our spacing, seeing where the advantages are, and making the right plays.”

So did Jayson Tatum.

There was complete consensus from the three Celtics’ that spacing issues cost them this one.

At its core, spacing is the concept of offensive players making sure there is enough room in between defenders — the strategic positioning of players to create open space for passing, driving, and shooting.

I asked Joe Mazzulla about what he thinks the roots are of the team’s poor spacing — and what exactly the Celtics need to do to rectify things in real time.

“It’s just something you got to commit to every possession as you’re playing a game and going through it, and looking to process each possession,” Mazzulla said. “You just got to fight for great spacing every possession. Sometimes, different matchups and different coverages will mess it up.”

Joe Mazzulla referenced one example of the team’s offensive spacing breaking down.

“We ran a pin-down, and they got it and it was empty-side, and we didn’t get the corners filled, and they were able to take advantage of that,” he said. “So, a large portion of that is just kind of the discipline and continuing to do it over and over again each possession — as you try to work through the flow of the game.”

Jayson Tatum gets banged up in fourth quarter spill — but walks away okay

Tatum took a nasty fall out of bounds chasing after a loose ball in the third quarter and stayed down for a minute in pain. Joe Mazzulla and a few of Tatum’s Celtics teammates crowded over him for a moment, but Tatum stayed in the game and scored 9 of the team’s 12 fourth-quarter points.

After the loss, Tatum shared that he simply bruised his forearm after jamming into a chair on the sideline.

“I’ll be aight,” he said.

That’s a welcome sign for the Celtics, who played just their second game all year with their entire rotation healthy. A game against the Nuggets is up next in the Celtics’ difficult four-game road trip; they traveled to Denver after Sunday’s loss.

And unless Tatum is on the injury report on Monday, the Celtics’ should have their full roster healthy for the second straight game as they look to get back on track on Tuesday.