The rebounding problem is overblown.
First off, the Celtics system emphasizes getting back on defense instead of hitting the offensive boards. Due to the system I think the offensive rebounding numbers and thus the overall rebounding numbers aren't a big deal.
Since the 6th game of the season the Celtics have been the 15th best defensive rebounding team in the NBA. Since we knew rebounding would be a problem coming into the season, middle of the pack rebounding shouldn't be a cause for concern.
For a long time, elite big men have been the most difficult asset to acquire in the NBA, I think the poor rebounding over an extended span has to do simply with not having one of those because we weren't picking high in the draft rather than a failure by Ainge.
It's extremely important. We take a LOT of threes on this team. Threes are the lowest percentage shot in the game, so a lot of threes attempted means a lot of rebounds available. If we aren't grabbing those rebounds, it means that the opponent is. Every rebound the opponent grabs is a free possession.
Allow me to demonstrate, roughly, what I'm saying here.
Our team average 31 three point attempts per game and 11 three point makes per game. That means that this team averages
20 three pointers missed per game.
Our team averages
9.3 offensive rebounds per game - lets round that up to 10, to be generous.
That means that every game we giving up 10 free possessions to our opponent as a result of missed threes. Lets say those 10 possessions average convert at an average of 1.5 points per possession for the opponent. Multiple that by 10 possessions, and that's 15 points we are giving up off missed three point shots alone.
Out average points allowed ranks 8th in the East, at 102.6 per game. If we grabbed two more offensive rebounds as a team, we are taking away two opponent scoring opportunities, at an average of 1.5 points per possession, adding up to 3 less opponent points per game.
Our points allowed then drops to 99.6 points allowed per game, which would rank us as the second best defence in the East.
Now these numbers are hardly super scientific so don't quite me on exact positions and estimates - this is purely a point I'm making to demonstrate that the Boston Celtics rank
5th in the NBA in three pointers attempted, and
22nd in the NBA in offensive rebounds.
When you take a ton of threes and don't don't go after offensive boards, then you are basically giving up free possessions and bleeding points.
So yes, we need improved rebounding - desperately.
To make matters worse, we desperately lack any kind of post presence on offense, since Amir can't play anymore, and Horford/Jerebo/Olynyk are all stretch bigs by nature right now. This means nobody (bar Thomas) puts any pressure on the interior defense, allowing opponents to comfortably spread out defensively and smother out outside shooters. This drops out three point percentages because we need to take tougher shots, which only
exaggerates the impact of our poor offensive rebounding.
If we had a post scorer to draw consistent double teams, then maybe we could force the defence to collapse more, hence giving our shooters more space. More space means higher shooting percentages, which means less misses, which means less offensive rebounds - hence rebounding becomes less critical.
But we torture ourselves because we have no post presence, we have no rebounders, and we take a billion long jumpers every night. It's like putting a gun to your head and pulling the trigger.
My suggestion is we go hard after a Greg Monroe trade. He's barely playing in Milwaukee, and with a career average of 3.1 Off Rebounds per game (in 30 minutes), he's twice as good a rebounder as anybody else on this team. He's also a very good post scorer who would demand double teams ever time he touches the ball down low, and he gets to the line at a pretty beastly rate too (career 36.7% FTR). Monroe is also a good locker room guy and an outstanding passer who would fit nicely in to the Celtics 'ball movement' style of offence.
Monroe can likely be had for a modest figure, and he'd be a near perfect complement for Horford, who (as a versatile defender who is quite mobile, an excellent outside shooter) would very nicely cover all of Monroe's flaws.
Of Mornoe can't be had easily enough, then I'd look at pursuing Nerlens Noel.
Failing that I would even contemplate (at a stretch) taking a shot a Jahlil Okafor - the latter isn't a great overall rebounder, but his offensive rebounding was actually pretty solid last year, and he's a definite presence down low. Horford would also somewhat make up for Okafor's poor footspeed and horrendous defence.
What's for sure is that we need a proper, traditional big man on this team to play alongside Horford - who is very much looking like a rich man's Kelly Olynyk.