Anthony was quite simply not going to play with so many younger bigs ahead of him on the roster. Centers Tyler Zeller and Vitor Faverani require playing time, as do power forwards Kelly Olynyk, Jared Sullinger, and Brandon Bass. Since Boston plans on playing small more often this season, there just wasn't room for Anthony.
For Detroit, the story is similar. Bynum has fought with a nagging hamstring injury throughout training camp that has dropped him down the depth chart, "way behind" veterans Brandon Jennings and D.J. Augustin.
The trade speaks to just how much the Celtics like rookie Dwight Powell, who was acquired from the Cleveland Cavaliers in a transaction earlier this year. The No. 45 pick in June's draft hasn't played much in the preseason, but he has flashed positional versatility in his spurts on the floor.
With 16 guaranteed contracts on the roster, Boston would've needed to cut Anthony in order to keep Powell. That's why it's likely that this trade is being made with the intentions of simply saving cash, since Bynum makes about $900,000 less than Anthony.
If Boston chooses to cut Bynum, they save themselves a little bit of money and stay under the tax line, but it could also point towards the end of the Phil Pressey era, who makes about $3 million less than Anthony.
However, it would be surprising if they'd choose to keep the 31-year-old Bynum over Pressey, 23, simply for money reasons. The team would have to view the veteran Bynum as a significant upgrade, which likely isn't the case since Pressey is already a superior distributor.
No matter what happens next, this is another minor move made with the intentions of building a versatile roster that stays under the tax line.