The reality is, historically the on/off differential is the greatest indicator of importance and value to a team. Time and time again it is the one stat that doesn't really lie
Do you know which starter was our leader in net rating (I.e., point differential per 100 possessions) was?
Daniel Theis, and it wasn’t close.
Strangely, I’m not sure he was our most important or valuable player last year. But, the numbers don’t lie, I suppose.
And the fact that they both start, have played similar minutes, etc. and have that sort of discrepancy is incredibly telling. And for the record the leaders in that stat entering the game tonight were Tatum, Teague, Pritchard, R. Williams, and Semi with the latter 4 all playing between 116 and 185 minutes. While the 5 biggest minute players in the negative are Brown, G. Williams, Thompson, Smart, and Theis. Obviously you can't put much stock in this year as the sample size is small, but the last 2 years don't lie. That is plenty of time for these things to even out if they are going to and they just didn't. Tatum incredibly important, Brown not so much.
How are minutes distributed / staggered when Brown and Tatum aren’t playing together? Who are their teammates they most regularly play with?
You cite to two years ago, when Tatum was playing as a starter and JB was trying to stabilize the bench. Is there any wonder why Jaylen’s +/- is worse than JT’s under those circumstances?
Theis on/off differential per 100 possessions last year was +0.5. The players with at least 1000 minutes last year, the on/off differentials were
Tatum 11.1
Hayward 4.1
Smart 1.3
G. Williams 1.0
Theis 0.5
Walker -0.7
Brown -0.8
Wanamaker -1.6
Ojeleye -9.5
Here is Boston's record in the full games those players missed.
Tatum 2-4
Hayward 14-6
Smart 9-3
G. Williams 1-2
Theis 6-1
Walker 11-5
Brown 10-5
Wanamaker 0-1
Ojeleye 2-1
What is incredibly apparent from those lists is Boston needs Tatum. They've always needed Tatum, but they haven't really needed anyone else. The team does just fine when it misses anyone not named Tatum. I mean here we are sitting at 6-3 this year and Walker hasn't even suited up yet. He is the 3rd best player on the team, and yet the team just keeps right on trucking along as if he is there. The last 2 wins, no Teague either. Doesn't matter. You take Tatum out though, it matters. He is Boston.
I think this is partially true but I see the conclusion differently.
The team has brought the two players along very differently. Tatum always has the ball nearly twice as much, and the offense has increasingly run through him. Until this year, Brown's only avenue was to be opportunistic. Even now, the ball does not stick with him, and he doesn't usually start plays even with Tatum on the bench.
That does create a dependency. When Brown comes out, no one else is looking around wondering who starts the offense. Especially without Walker, Tatum is doing most of that work. Even when Walker is playing, he's more of a scorer than a playmaker.
My guess is if we had one or two more ball handlers that were any good, the value would even out. But the C's don't really have playmakers. Who is more valuable is situational. If, let's say Pritchard continued to improve and became a quality playmaker, or we traded for one, the dependency on that part of what Tatum does would go down, and Brown's ability to score in volume without needing to dominate the ball would be more valuable.
Brown has been asked to be a swiss army knife. He's never complained, and has instead figured out how to make it work, without worrying about perceptions about his status as a star. I expect him to be just as good as Tatum over the next few years, and I think they both make All NBA teams.