Since Donatas Motiejunas entered Houston’s starting lineup, that particular five-man unit has allowed just 95.6 points per 100 possessions. It’s an elite figure, but the sample size is far too small to attribute it any meaning.Motiejunas has played only 11 games with Jeremy Lin, James Harden, Chandler Parsons and Omer Asik beside him on the court. Here are the teams they’ve gone against: Nets, Wizards, Bucks, Magic, Mavericks, Warriors, Suns, and Timberwolves. Two of those teams boast top 10 offenses (barely), two are average, and the remaining four all find themselves ranked at or near the bottom.For this entire season, Houston’s defense has been inadequate. Despite harboring one of the four or five best defensive centers in the game, along with a few players on the perimeter who can be disruptive on the ball, the Rockets have yet to figure out a consistent method to slow opposing offenses down. They allow 104.3 points per 100 possessions, making them the 10th worst defense in the NBA.The good news is that most of their problems are correctable, or so it would seem. A vast majority of the open shots Houston allows are due to various mental mistakes: ball watching, losing track of shooters, failing to know when it’s time to shoot the gap and when it’s time to stick to your man, needlessly helping in the paint when proper help is already there.These are all mistakes the Rockets make constantly, but all can be fixed. They don’t require an upgrade in skill or personnel, but more a change in mindset when it comes to defensive discipline. The Rockets are the youngest team in the league, so to watch them still endure growing pains shouldn’t be a surprise. Here are several examples.Here we have Jeremy Lin standing at the free-throw line, leaving his man, Ricky Rubio, wide open behind the three-point line on the left wing. He’s there to help prevent a wide open driving lane for Timberwolves center Greg Stiemsma, who’s operating a side pick-and-roll with Luke Ridnour.Knowing the situation, is this really necessary? Let’s say Stiemsma catches the ball in motion at the right elbow. Then what? Even if Lin isn’t there, there are two back line defenders (Motiejunas and Parsons) plus the quick-footed Asik there to help. Also, Stiemsma isn’t good.Here’s what happens:Timberwolves forward Dante Cunningham sets a back screen on Houston’s unsuspecting point guard, and Rubio is sprung for a wide open three ball. To Lin’s credit, this isn’t the most egregious play, being that Rubio is shooting less than 20% on three-pointers this season. But that doens’t mean he couldn’t position himself better.The first clip of this article features James Harden, Houston’s best offensive player and worst defensive player. We’ve seen this type of indifference from him all season. This play in particular is alarming, but easily preventable if he wants to prevent it.Rubio takes a contested pull up jumper on the right side of the lane, and off Harden goes, out past the three-point line looking for a quick fastbreak opportunity. As the Timberwolves grab the offensive rebound, Harden is still backpedaling towards the other end. Why? Well, he wants the easy basket on the other end, that’s why. And if you’ve ever played basketball before, can you really blame him? The play results in a wide open mid-range jumper for Luke Ridnour; the type of shot he could swish with both eyes closed while fixing a sandwich.More on Harden later.The next guilty party is Chandler Parsons, a player whose great overall skillset is often overlooked thanks to an uber-team friendly contract. In his rookie season Parsons began to make a name for himself as an incredible on-ball defender, and his work on Kobe Bryant and Kevin Durant drew praise from both players.This season Parsons has taken a minor step back on the defensive end; most of it is due to his random action away from the ball.Rubio has barely penetrated past Lin and his reward is a rushed look at a snarling Asik. Look where Parsons is standing. Why did he drop so low, leaving Mickael Gelabale beyond wide open on the perimeter? (Gelabale is shooting 52.5% on the season.)The play ends with Minnesota taking full advantage of Parsons’ mistake. Rubio swings the ball to Gelabale, who passes it to a wide open Stiemsma on the baseline after Parsons retreats for a late close out. Stiemsma sinks the shot.But Parsons’ troubles don’t just come with weakside help. Here he is later on guarding Gelabale. Rubio sets a pin down screen but instead of following his man above it, Parsons cuts beneath, then unnecessarily runs into a second screen set by Stiemsma. Here’s the play:(Before we finish up with one more play from Harden, I’d like to point out that the Rockets would be in the lottery if not for his work on the offensive end. Harden’s defense needs work, sure, but his effort with the ball is an irreplaceable commodity, and it’d be an honest shame if he didn’t end up in fourth or fifth place in the final MVP ballot. For all the gushing praise Dwyane Wade and Kobe Bryant receive for their play this season, Harden undoubtedly belongs in their class at the shooting guard position. Okay, now back to jumping on his defense.)If I hadn’t already pointed out the play where Harden leaks out instead of staying with his man, could you even guess who he’s supposed to be guarding right now? Look at it in real time:Harden is helping on a Stiemsma roll to the basket, but similar to the Jeremy Lin play from before, is his positioning a bit dramatic? As Rubio takes a dribble to the left, Harden hades more towards the middle of the court even though Motiejunas is already in the paint. Meanwhile, Harden’s man, once again Ridnour, drifts to the corner. Completely ignored. The ball is eventually swung to him and he hits the shot.All these decisions by Houston’s defenders come with the strategy of packing the paint, disallowing penetration or anything easy near the rim. But they also all come with Omer Asik on the court, and what’s the use in over helping when you have a guy like that protecting the rim? (Asik is out on the perimeter guarding pick-and-rolls in a couple of these examples, but if the Rockets are so concerned with their interior defense in these situations maybe they should have Asik sag below the free-throw line to help contain the ball-handler whenever the opposing center isn’t all that great a risk of popping out for a jumper.)Some of these open shots might be the result of scheme, but others simply aren’t smart basketball. Even after the Rockets make their run at a secondary All-Star caliber player, if they don’t clean up their defensive miscues a championship won’t be in the cards.