The Celtics (8-8) didn’t just lose on Friday night - they stumbled through what may go down as one of their ugliest defeats of the season, falling 113-105 to a struggling Nets (3-12) team in NBA Cup pool play. Boston looked in control early, but everything unraveled the moment the game demanded poise and execution.

What started as a manageable back-and-forth affair spiraled in the third quarter once Jaylen Brown was forced to the bench with foul trouble.

Brooklyn immediately seized momentum with a crushing 19-4 run, ballooning their lead into double digits and stretching it to 18 as the Celtics completely lost their grip on the game.

Boston’s late push - a 15-4 burst to open the fourth - gave the illusion of a comeback, but Michael Porter Jr. closed the door with a series of daggers as the Nets delivered the knockout blow.

Brown led Boston with 26 points, and Anfernee Simons provided 23 off the bench, but it wasn’t enough to overcome a Nets team powered by Porter Jr.’s 30 points and Nic Claxton’s triple-double (18 points, 11 rebounds, 12 assists).

The Celtics fell to 1-2 in Group B play, essentially eliminating them from NBA Cup contention, and dropped back to .500 on the season.

Here are four takeaways from a brutal loss in Brooklyn:

1. Flat, sloppy basketball buries Boston early

If there was a theme to this loss, it was carelessness.

The Celtics looked disconnected from the opening tip, repeatedly botching defensive coverages and giving Brooklyn uncontested looks at the rim.

Offensively, the focus wavered just as badly - headlined by Josh Minott’s ill-fated decision to force a pass on the final possession before halftime, a giveaway that led directly to Nets points and earned him a second-half benching.

The larger problem, though, was the total lack of defensive urgency, which put Boston behind the 8-ball long before Brooklyn’s big third-quarter surge.I feel like I keep writing the same thing over and over again, but the loss of guys like Jayson Tatum, Al Horford and Jrue Holiday, especially defensively, is glaring through 16 games.

2. Jaylen Brown’s fifth foul triggers the collapse

Boston was already teetering, but everything fell apart the instant Brown picked up his fifth foul midway through the third.

Joe Mazzulla gambled by keeping him on the floor with four fouls, but once Brown was whistled for an offensive foul - a call Mazzulla unsuccessfully challenged - their offense and poise vanished.

The Nets pounced, ripping off a decisive 19-4 run that turned a tight contest into a near-insurmountable deficit. Boston never fully recovered, even with its fourth-quarter push.

Brown’s night falls right in line with what he’s been saying postgame the last few games. He continues to end games as Boston’s leading scorer, yet the eyeball test will tell you that it’s not exactly an A+ effort from the 2024 Finals MVP. I know I gave him a B- on his latest progress report, but I’m starting to think I was too easy a grader.

Brown was critical of their effort during his postgame press conference:

3. Anfernee Simons injects badly needed offense

On a night when Boston’s backcourt sputtered, Simons nearly stole the game himself.

The reserve guard hit 10 of his first 14 shots and was lethal inside the arc (8-of-10), delivering one of his sharpest scoring nights as a Celtic.

His burst helped erase much of the 18-point hole early in the fourth quarter and gave Boston a fighting chance - one the rest of the roster couldn’t capitalize on.

More on him in a bit.

4. Derrick White’s prolonged shooting slump deepens

White’s early-season struggles resurfaced in a big way.

The Celtics desperately needed steady offense with Brown in foul trouble and the game slipping, but the starting guard couldn’t provide it, finishing 2 for 13 from the field and 1 for 7 from deep.

Against the NBA’s worst defense, Boston repeatedly generated clean looks for White that simply didn’t fall. He ended with just 6 points, and the Celtics couldn’t withstand such a quiet night from their No. 2 scoring option.

Simply put - White is having a bad 2025-26. It’s becoming more and more clear by the day that he’s someone who profiles more as a third/fourth option than a second. They need more from him to have a chance at anything postseason-wise this year.

Lingering Thoughts & Nuggets:

- Brown was mad at the refs postgame. I would have preferred if all the anger for him postgame was directed at both himself and the team instead. No need to passive-agressively point the finger when you’re losing at home on a Friday night in front of a packed house to one of the worst teams in the NBA. Whether the refs were good or bad, it doesn’t change the result after the fact. This energy makes it seem like you’re not focused on the right things.

- I’ve said it on RTB before and I’ll say it again - it’s time to get Simons in the starting lineup. I don’t care how much of a liability he is defensively. They need to switch up the vibe, because this ain’t it. With the Magic (9-7) on deck, I think it’s the perfect time to give this a shot. Simons played very well against the Magic just a few weeks ago down in his hometown of Orlando.

- It was only game No. 16 on the season, so I’m not going to sit here and tell you Friday night was a “must-win” situation for the Celtics. But with the upcoming schedule the Celtics have directly following this one, it certainly felt like a “gotta-have-it” situation for the green:

11/23 vs. Orlando (8-7)
11/26 vs. Detroit (13-2)
11/29 @ Minnesota (10-5)
11/30 @ Cleveland (10-6)
12/4 @ Washington (1-13)
12/5 vs. Lakers (11-4)
12/7 @ Toronto (10-5)
12/19 vs. Miami (9-6)
12/20 @ Toronto (10-5)

Outside of that Washington game, that’s an absolute gauntlet before hitting a softer part of the schedule around the holidays. I feel like getting this one would have been big for their confidence. Instead, we have to sit here and wonder whether or not Mazzulla needs to mess with the starting five to get something going for this team.

Frustrating stuff.

- On a lighter note, Michael Scott was in the house! The famously bad TV boss was seated courtside next to Celtics new boss Bill Chisholm. And if we're being honest, all Chisholm has done so far as owner is employ one of Dunder Mifflin's prevailing corporate themes throughout his short tenure: downsizing (à la moving on from three of the team's best players to get under the apron).

Tom Carroll is a contributor for Roundtable, with boots-on-the-ground coverage of all things Boston sports. He's a senior digital content producer for WEEI.com, and a native of Lincoln, RI.