The Boston Celtics are known for being a team that wins games with their defense.
They normally have flawless rotations, smooth help and lockdown both the interior and the perimeter at critical moments. However, that has not been the case for the first quarter of this season.
To be fair, the Celtics' defense has improved significantly over the past several games, and is coming much closer to resembling the type of D that got them to two NBA Finals in five years.
Regardless, improvements still need to be made on that area of the floor.
It's important to understand where those primary improvements need to take place, so let's examine how teams have been attacking Boston this season.
Let's first take a look at what Jerry Stackhouse did to the Celtics in their second meeting with the Brooklyn Nets.
Stackhouse drained five three-pointers in this game—the last four were essentially wide-open looks as the result of poor closeouts by the Celtics.
You'll notice that the second trifecta he hit came off of an offensive rebound, an area where Boston has struggled mightily this season.
Andray Blatche grabs the board with literally all five of Boston's players in that area. That is unacceptable, as it leaves a knockdown shooter in Stackhouse wide open from the corner. By the time Jeff Green ran out to defend the shot, it was too late.
The third three-pointer was a result of lazy transition defense, and the fourth and fifth were the product of over-helping by the Celtics' defense.
Over-helping is an issue that Boston has had for most of the season, as it has led to poor rotations and late closeouts.
Opponents are taking advantage of this and are catching Boston sleeping. It's not just three-pointers, though—too many times, this has resulted in wide-open layups.
What else has ended up in easy buckets for opposing teams? Getting beaten on dribble penetration.
A good example is the Celtics' third meeting with the Milwaukee Bucks this season.
Go to 1:11 in this video. You'll see that the Celtics have a three-point edge with just over a minute to go.
Courtney Lee is taken off the dribble by Monta Ellis. Because Lee was beaten, Kevin Garnett has to step up. That leaves Larry Sanders wide open for an easy dunk. Those types of things just cannot happen at that stage of the game.
It gets worse.
On the Bucks' next possession (it starts at 1:24), Lee gets beaten off the dribble by Ellis again. This forces Garnett to step up, forcing Paul Pierce to then stick to Sanders. As a result, Marquis Daniels is left wide open in the corner.
You'll notice that both Pierce and Jason Terry rush to close out on Daniels (a lifetime 23.1 percent three-point shooter).
Terry makes the mistake here by leaving Brandon Jennings. There is absolutely no need to have two guys closing out on someone who isn't even a threat from long range, especially when you're leaving an opponent's top-two scorer open.
Daniels sees the gaffe by Terry and quickly dishes the ball to a wide-open Jennings, who nails what would ultimately be the game-winning three.
There were all sorts of problems on that possession—from Lee getting taken off the dribble to two players closing out on a poor shooter to ignoring Milwaukee's second-leading scorer.
Here is another clip that demonstrates some of Boston's defensive struggles.
At the 1:26 mark, you'll see the Celtics' defense out of sorts thanks to a simple screen. Tiago Splitter picks Leandro Barbosa, forcing Garnett to help.
The problem is, Barbosa and Garnett then run into each other, allowing Boris Diaw to rifle the ball to Splitter for an uncontested dunk.
Teams are attacking Boston in these different ways because they have seen how vulnerable Doc Rivers' ballclub has been in these areas.
The C's are getting beat on dribble penetration and pick-and-rolls, and just can't seem to rotate effectively.
Sometimes, you simply have to give the other team credit for making plays. However, these types of hiccups were not happening to Boston over the past several years, at least not nearly as often as they have this season.
In the past, Boston's communication on defense was excellent, and rarely did you see blown assignments.
That being said, the Celtics have a lot of new faces on the roster this year, so the lack of proper communication is understandable.
As stated earlier, the defense has been getting better as of late, and that is to be expected. Boston still needs time to gel and learn each others tendencies, and you can see that beginning to take shape now.