A few assumptions:
1) The Celtics will want to stay competitive, that means getting a player who could at least conceivably be an all-star next year as the main return in a trade.
2) Teams who are trading for Brown want to win, an they can?t do that if they gut their team and have nothing left but brown after a trade. A Brown trade ha to make sense FOR BOTH SIDES.
With that in mind, a look at every team?s interest in Brown:
ATL- What?s the piece they are sending back? Jalen Johnson is the guy they?d want to pair Brown WITH, its not going to be him. Their offer would be more of a poo-poo platter of picks/young guys, none of which do much for me if I?m Boston.
BRK- MPJ would be the main piece coming back, but trading an All-NBA guy for an expiring sub-all star with an injury history doesn?t seem like a great idea.
CHA- Made more sense before the LaMelo trade. Brandon Miller might make sense as the primary piece coming back whom the Celtics could dream on being an all-star, but I just don?t think Charlotte is going this direction. Creates a situation where their two best players (Brown/Kon) are ten years apart in age. That doesn?t make a lot of sense to me for them.
CHI- No primary piece coming back that?s good enough to intrigue the Celtics.
CLE- Mobley could be the main piece, he?s that all-star borderline all-NBA return you?d want in a Brown trade. But with Mitchell/Harden already as ball handlers and being in the 2nd apron it?s hard to see them doing that deal. Brown-Mitchell meanwhile doesn?t change a lot for either team, just makes Cleveland MORE expensive.
DAL- No primary piece coming back that?s good enough to intrigue the Celtics.
DEN- They have cheap ownership, it?s hard to see them trading for a guy on a 35% max with how frugal they?ve been lately. Trading Brown for Murray just makes them MORE expensive, so I can?t see that happening.
DET- So this one makes some sense if Duren is the guy coming back. A S&T with him and Brown could make some sense. But seeing as how they just decide to trade their very good backup center away for almost nothing I have a hard time seeing them completely emptying their front court to get 7 years older and dramatically more expensive. No other primary piece that?s really interesting there, picks aren?t worth much either.
GSW- No primary piece to put in the trade.
HOU- Durant is a thought, but trading a 30 year old for a 38 year old doesn?t feel like a great idea to me. A trade here depends entirely on what you think of Sengun because that would be the main piece. I?m not particularly fond of his game as I don?t put a lot of value in mediocre defensive centers, especially ones that aren?t all that efficient, but maybe Brad Stevens feels differently.
IND- This is another team that fees unlikely mostly because the ownership is just not going to greenlight enough spending to fit Jaylen into their salary structure.
LAL- No primary piece to put in the trade. Boston isn?t doing a Kawhi for Brown trade with Kawhi in the last year of his deal and rumors he?d only re-sign for TOR or SAS. Not to mention the Aspiration scandal still hanging over him. Garland has no value right now with his injury issues.
MEM- They just started a rebuild, not in the ?acquire star player? phase. And no, Morant will not be the main piece, he?s a negative value asset let alone the main value in a Brown trade.
MIA- If Bam was the main piece coming back then maybe, given how much Mia loves Bam that?s a 0% chance.
MIL- No, for obvious reasons.
MIN- No, just acquired LaMelo.
NOP- This is the most often rumored one an the one that makes SOME sense. Trey Murphy would be the primary return. The issue here is Trey Murphy as good as he has been is still a sub all-star type of player and how much more does NOP want to give up? Keep in mind the idea for them would be to compete, and if that?s the case they aren?t going to want to include other important guys in the offer. You aren?t getting three of Trey/Murray/Zion/Herb. It guts their team and defeats the purpose of acquiring Brown in the first place. Puts aside the fact the Murray is coming off a major injury and Herb wasn?t actually good last year so why would you want them anyway. It?s probably Trey Murphy, salary filler, and picks. Is that good enough? Depends on what you think of Trey Murphy.
NYK- No, for money reasons and vibes.
OKC- No, for money reasons they literally can?t.
ORL- If the primary return would have to be something like Franz (or Paolo) and WCJ to make the money work. That?s at least theoretically something both teams might consider, but I imagine ORL doesn?t think Brown is worth 16+ million more than Franz or even if they do its not worth getting 5 years older and giving up their starting center to do so.
PHI- No, George/Embiid would have to be in the return for money reasons and the Celtics aren?t touching those contracts with a 10 foot pole.
PHO- No primary piece to put in the trade.
POR- Okay, here?s another one that?s often rumored. I?d assume Deni is not an option because that?s the guy you want to pair Brown with. That means it would have to be a young guy/picks type return. So if Boston is looking to remain competitive that doesn?t make a lot of sense. This team made more sense as part of a three-team deal with Mil, seeing as how that didn?t happen I can?t see Jaylen getting traded there now. Boston would have to believe A LOT MORE than league consensus in Sharpe/Clingan for this to make sense because that and picks woul be the main return. A POR trade really only makes sense if Boston is okay taking a step back next year.
SAC- Sabonis would have to be the main piece coming back, and he?s just not good. I?m sorry, I do not understand people?s fascination with him and I trust Brad to feel the same. Hard no.
SAS- It would likely have to include Fox coming back to Boston for money reasons. And Fox is a good player, but I just can?t see Boston being interested in that contract/position combination. The league is PG saturated right now, paying the max to one is simply not a good value. This is a team that just made the finals so I have a hard time seeing them blowing up the foundation of their team for Brown. I? imagine Castle and Harper are off the table given what they showed this post season run, I don?t think you trade either for a 30-year-old vet making 57 million. Future is too bright here for a big swing IMO.
TOR- Not much of interest there accept Barnes and they aren?t trading Barnes, again he?s the guy you pair Brown with to have a chance.
UTA- For Lauri it might make some sense. Lauri is only a year or so younger than Brown, and maybe UTA thinks Brown is a better fit next to JJJ/Kessler. Problem is Lauri has played worryingly few games over the last few years and been somewhat inconsistent. He?s a big risk to take as the primary return in a Brown trade, but he?s talented enough that if its him an other stuff maybe you consider as Boston. Still it feels like this team is going to see what they have with their super-sized front court and Peterson before making another big swing. Depends a lot on what you think of Lauri.
WAS- Anthony Davis?s trade value last trade deadline was fake first rounder(s) and salary relief, he?s not going to be the main return in a Jaylen Brown trade. Too much injury risk. No other real path to a deal here.
Conclusion: Trey Murphy from NOP, Alperen Sengun from HOU or Lauri Markkanen from UTA seem like the three most likely targets that would make some sense as the main return for Boston. Franz from ORL or Duren from DET are also outside possibilities, although I think those teams are less likely to be interested given the large age difference between those players and Brown.
The main point here is it is hard to find a deal that makes sense. Star for Star (or Star for Really Good) player trades are always difficult especially if both teams have aspirations to compete. The deal becomes more workable if draft picks are the primary thing coming back, but would Boston be willing to take a year or two off from competing in the heart of Tatum's prime on the hope that in a year or two they can chase a star with those draft picks? Hard to say.