We don't even know if the deal is official yet (Kevin Garnett has waived his no-trade clause, making the deal agreed to in principle) but here's a quick look at what it could mean to the Celtics.
Let us start with the rumored details.
Going out: Paul Pierce, Kevin Garnett, Jason Terry
Coming in: Gerald Wallace, Kris Humphries,
Tornike Shengelia, Reggie Evans, Keith Bogans (via sign and trade), an unnamed minimum salary player, and 3 first round draft picks (2014, 2016, 2018)
Update: the Celtics will get Kris Joseph and Marshon Brooks instead of Shengelia and Evans. There are also reports that they have the right to swap picks in 2017 - but not confirmed.
What's the Net's rationale? Making a run at the title right away. They have an owner that will spend what it takes to get what they want and they are willing to give up future picks (that they hope will be low anyway) to get what they need now.
What is the Celtics' rationale? Blow it up and get the maximum amount of assets (read: draft picks) to start the rebuilding process quickly.
Emotionally this is a huge blow. On the other hand, most have seen this day coming for a while now, it was just a matter of time. This was Danny Ainge's chance to start over and get something for KG and Pierce before they walked away for nothing so he took it. But that doesn't really soften the blow too much. It hurts to see Doc Rivers go. It hurts to see Kevin Garnett go. It really, really, really hurts to see Paul Pierce go. The only thing that makes it feel a bit better is that all three now (apparently) have indirectly contributed to hopefully strengthening the position of the team going forward into the new era.
Which brings us to the business side of things. Gerald Wallace was once a really good player. Good enough to get a couple of big contracts. He still has three years and over $30M on his contract and he's no longer worth anywhere near that money. However, the team seems willing to take on that contract in order to gather up the 3 draft picks.
You see, in a rebuilding effort, draft picks are gold. You can either use them to select good, cheap talent with upside potential, or you can use them to complete trades for veteran talents (like Ainge did when he traded for Ray Allen and Kevin Garnett in the same summer).
Earlier in the summer it was thought that Danny's asking price for Pierce and Garnett would be about a draft pick each. In this proposed deal, the Celtics get three first round picks.
In addition, some teams wouldn't have taken Jason Terry's long contract without getting a draft pick along with him. Instead, the Celtics take back a little more long term salary in the form of Wallace's deal, but they are not going to be competing next year (at least) so they'll have to pay someone.
I always liked Reggie Evans and I'm sure Kieth Bogans has his qualities as well, but those guys are mostly in here (I imagine) for salary matching purposes.
Again, the bottom line is that Celtics decided that the Celtics, as they were constituted at the end of this year, were no longer contenders. They wanted to turn the page and start over. How much of that caused Doc Rivers to leave and how much of Doc's exit prompted this bold move is anyone's guess but the people involved. But I tend to think they were intertwined.
So the Celtics move on with a nucleus of Rajon Rondo, Avery Bradley, Jeff Green, Jared Sullinger, and lots of draft picks. They'll either build their core slowly (like the Soincs/Thunder did) or make another bold move in a year or two (or who knows, maybe sooner) like Ainge did to assemble the Big 3.
Two big unknowns going forward are 1) will the team commit to building around Rajon Rondo and 2) will they be bad enough to be in the running for a high lottery pick in next year's stacked NBA Draft. Time will tell, but those are questions for another day (probably tomorrow - so stay tuned).