Brook Lopez has been a monster this year, that is for sure, but if you wanted to nit-pick, you could say that he has struggled in the second half. There has been a noticeable drop-off in Brook's second half scoring when compared to his first half scoring. A lot of it has to do with lack of execution, but some of it is just circumstance.
To figure out some stuff what's different from the first half to the second, we are going to look at some screen shots (these clips are all from the Nets-Cavs game where Brook put up 20 in the first half and 2 in the second. I noticed a lot of the same things in other games though). The first thing that I noticed is team's usually don't put their big man on Brook unless he is a solid defender, early in games. Teams usually want to prevent their starting centers from getting in early foul trouble (like what happened early in the Laker game. They put Bynum on him early, and he spent much of the game in foul trouble). The Nets and Brook take advantage of this a lot.
The next thing is the lack of execution. The key to preventing double teams from arriving early is movement. When players move without the ball, defenders have to stay focused on them, and it is hard to double down on the big man when you don't know where your man is. This being a relatively young team, they tend to lose focus every once in a while. This loss of focus usually happens in the second half. When you start the game, you usually execute to perfection because the coach's speech is still fresh in their mind.
The final reason for Brook's drop-off in the second half is that the Nets' have been behind by double-digits in most of these games. When teams come from behind like that, they usually don't throw the ball into the post. They try to run and gun and tend to jack up threes which is what the Nets tend to do. Also, a few times, Kiki has pulled Brook in the middle of the fourth quarter because the game was out of reach. Not being on the court hurts his production.
Let's look at the Cavs game:
Alright here Brook gets the ball and the first thing you notice is that J.J. Hickson is covering him. This is an absolute mismatch. The next thing to look for is the movement. Devin Harris after making the pass will cut through the paint. His man naturally has to follow him, so Devin's man can't double on Brook. Courtney Lee also rotates to the top of the key, to draw the defenses attention away from Brook.
The double team triple team eventually comes, but if you look at this, you notice Brook has already made his move to the basket. Because of the Nets' movement, the triple team comes too late. Usually they would like to get there as Brook is still dribbling, to prevent him from getting close to the basket.
Because he is so close to the basket, Brook is able to rise up, and finish strong. Now let's look what happens in the second half. Now, let's take a look at the second half:
This is the first Nets' possession of the half. Notice anything different? Shaq is covering Brook. The pass gets made, and because Shaq is on him, Brook doesn't look to score and quickly kicks it out.
This is the second possession. Shaq is covering him again, and this time Brook wants to score. Notice the other 4 Nets' and where they are positioned on the court. Mo Williams is already doubling before Brook makes the catch.
Courtney, after making the entry pass doesn't cut right away. I don't know if it was a mental lapse or just was planned that way, but the late cut doesn't clear the lane. Also, Trenton Hassell and Josh Boone are way too close to each other, allowing for one man to cover both of them. Since, LeBron can cover both of them, J.J. Hickson steps in the middle and doubles Brook.
This actually was a play to get Devin an open 3 point look, but it took too long to develop. Boone and Hassell should have been in position to set the screens sooner, and that would have forced LeBron to slide out on Devin, and that would have forced Hickson to defend both Boone and Hassell. That would have meant one on one coverage for Brook.
Brook can't get around Shaq because Hickson is standing in the middle, keeping that from happening. Because of that Brook decides to shoot a fall-away jumper. Since Shaq doesn't have to worry about Brook driving around him (J.J. Hickson is there to help him), all Shaq has to do is wait for Brook to pull up and time it to block the shot. That is exactly what happens.