Do the Rockets need an Elite Shot Blocker?

From the perspective of a player, when factors such as pride are involved, getting blocked is something that must be avoided at all costs.  The roots of modern basketball (and a great number of NBA players) trace back to pickup games and playground-style rules where fouls do not lead to free throws and getting blocked is a point of embarrassment.  The smarter players can overcome this instinctual aversion and understand that challenging defenders around the rim leads to more free throws.  Not surprisingly these players are said to be “fundamentally sound,” and often are products of excellent coaching or European influence.

On the other end of the court, one aspect of being “undisciplined” defensively, somewhat synonymous with being “raw”, is the uninhibited impulse to block every shot.   When there aren’t any refs, the risk-reward relationship of attempting to block a shot shifts significantly in favor of going for the block.  Concurrently, the influence of pickup basketball rules changes a player’s perceived risk-reward relationship between driving to the rim and pulling up for a lower-percentage shot.  When the opportunity of free throw attempts is removed, a slight boost in FG% for shots around the rim versus, say, a 10-foot jump shot, does not justify the immense social risk of getting rejected.  My hypothesis is that, despite logic and best efforts of a coaching staff to keep players “disciplined” offensively, many players in the NBA cannot control their aversion to getting blocked, and therefore attempt lower-percentage shots.  These low-percentage shots include, in order of increasing egregiousness: raising the arc on a shot to clear the shot-blocker, shooting a fade-away, altering the shot/shooting form in mid-air, attempting a “floater” when there is a possible lane to the rim, and avoiding the drive all together and jacking up a long 2-pointer.

Opponent Shooting Percentage vs. Team Blocks

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The first step in my analysis was to see if there was a correlation between team block rate and opponent shooting percentage.  The idea is that if your team blocks a bunch of shots, opponents will not only miss those shots that were blocked, but will also have a large number of altered shots (assumed to be of greater difficulty and a lower shooting percentage).   Looking at regular-season data from 1999-2009 (, there appears to be a decent relationship, as displayed in the graph.   As you can see, as a team blocks more shots (block rate is blocks divided by opponent’s 2-point FGA), their opponents shoot at a lower percentage (ρ = -41.08%, rsq = 16.9%).

Opponent Shooting Location vs. Team Blocks

So we know that there is a relationship between opponents’ shooting and team shot blocking.  That was the first part of the theory.  The second part was that the FG% is lower because of an aversion to drive all the way to the basket.  The best way to measure that is to compare team shot blocking to opponent shooting locations.  I compared team block rates to two different location attempt percentages defined by (2006-2009) – “at rim” and “<10 feet” (for example, the “at rim” location attempt percentage would be attempts at rim divided by all 2-point attempts; in other words, the percentage of 2-point attempts at the rim).    To my initial surprise, there was a slightly negative correlation between opponents’ at rim attempt percentage and team block rate (ρ = -12.38%, rsq = 1.5%).  It makes sense, as more chances to block shots will obviously result in more blocks; however the relationship is pretty weak.   I then compared the same team block rate to the “<10 feet” attempt percentage.  The results were even more unimpressive (ρ = -3.2%, rsq = .1%).

What does all that mean?  It means that, despite a team blocking shots at a high rate, opponents do not change their shot locations.  My theory that players will tend to stop short and pull up instead of go all the way to the rim when driving against strong shot blockers was incorrect.  They still will attempt those shots.

But what about the FG% thing?  I showed earlier that block rate has a decently strong relationship with opponents’ FG%.  I just showed that that relationship has little to do with shot location, so what else could it be?  Taking a further look at the breakdown in opponent’s FG% by location, you can see what is happening:

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To my best understanding, the biggest effect of strong team shot blocking is altering shots near the rim.  The closer an attempt is to the rim, the greater effect a team’s block rate has on opponent shooting.  For “at rim” attempts, we see the most drastic dip in FG% (ρ = -46.48%, rsq = 21.67%).  It seems that shot blockers also affect “<10 Feet” shots as well, but not as much (ρ = -32.99%, rsq = 10.88%).  Conventional wisdom preaches the benefits of shot blockers altering shots, but this is the clearest evidence actually supporting that claim.

Opponent Shooting Location vs. Best Shot Blocker (Elite Blocker Theory)

Despite my best efforts to encourage basketball viewership from a team perspective, it is widely more popular (and fun) to look at individual players.   After all, when you’re driving to the rim against the Magic, are you thinking about Orlando’s team block rate or are you thinking about Dwight Howard throwing your shot into the bleachers?   I scanned through the same four seasons, and found the leading shot blocker on each team each year (minimum 65 games), using blocks per game.  I chose blocks per game over block rate to place weight on minutes played.  After all, a player’s “presence” cannot be felt if he isn’t on the floor very much.  I then did the same comparison as the previous section.  Predictably, there is a similar lack of meaningful relationship between the best player’s blocks per game and opponent shot attempt location.  However, just like team block rate, there is a relationship worth considering for FG% at the rim (ρ = -35.99%, rsq = 12.95%) and FG% <10 feet (ρ = -19.46%, rsq = 3.79%):

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As you can see, having an elite shot blocker clearly affects opponents’ shooting, and can explain a large part of a team’s block rate, especially at the rim.   If you read my first post, you know how important shooting efficiency is to winning.   Good teams hold opponents to a low FG%, and good shot blockers hold opponents to a low FG%.  So, exactly how important is it that your team is good at blocking shots?

Block Rate to Wins

To keep this all in perspective, I compared block rate to wins from 1999-2009.   Compared to some of the more prominent categories discussed in past posts, blocks are not very significant.  However, there is a positive correlation, with an r-squared of 6.7%.   Here is a graph showing the relationship between wins and block rate:

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While blocking more shots may make a minor contribution to wins, it is directly related to one of the Rockets’ biggest weaknesses – opponent shooting. That weakness is further compounded by abysmal perimeter defense, allowing opposing wing players to penetrate with ease.

Through 11/17, opponents were shooting 63.7% at the rim against the Rockets, above the league average of 62.4%.   In case you were curious, Howard and the Magic are holding their opponents to 54% at the rim, the lowest rate in the league.

The bottom line is Jordan Hill needs more playing time.  All of this business about him being a liability offensively needs to stop.   He is shooting 70.8% on inside shots, with only 53% of them coming from assists (which means that he is creating about half of his own shots inside, and still shooting 71%; sounds pretty good to me).  As I mentioned last week, one of the biggest reasons he cannot stay on the floor is his poor court awareness and defensive rotations.  As soon as he can work out those kinks, I think he can provide the interior help that we have been lacking most of the season.

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  • zen

    With a record that currently sits in 29th place out of 30 teams, the Rockets need an elite everything.

    That being said, an elite defense is needed to win titles, but not necessarily an elite shot blocker. I’m looking at the champions of this past decade. Lakers? Some good defenders but not necessarily block-happy. Their length denies any easy passes into the lane for a high percentage shot. Spurs? Excellent defense, but hasn’t Duncan been their only blocker? Celtics? Again, good defense in regards to denying access to the paint, but were they known for a lot of ‘swats’? I’m not sure, I could be wrong. It looks like forcing opponents into shooting from a bad spot is more of the championship hallmark, but probably a harder stat to track.

    Dwight Howard is known as the best shot blocker these days, but he is in the wrong defensive scheme to really reach his potential. Orlando’s NCAA style of four guys on the perimeter and only Dwight in the paint means that he’s routinely outnumbered. I guess it says a lot that he still gets so many blocks and rebounds without a traditional PF beside him for most of the game.

  • Anonymous

    You did the best job I’ve seen of capturing the concept of “presence” statistically by distinguishing between per-game and per-minute stats.

    That psychological aspect to the game is something that is fascinating. A team can rotate as much as they want and lead the league in charges, but people will still keep taking it in because that fear isn’t there.

  • Stephen

    Perhaps the lack of effect of shot-blocking on the short-range shots is due to the shot blocker most often blocking a shot from another teammate’s man-ie a help shot-block,not a block of his own man’s.
    Most guards put a lot of arch on their shots in the lane anyway,so perhaps they’ve already adjusted mentally to the threat of getting blocked. But at the rim no one shots w/arch,so it’s both easier to get to the shot by a defender and often the shooter is contorting his body and trying to spin his shot in,something they would not do w/no pressure.
    Another effect a shot-blocker causes is the rushed dump-off pass. A player is going to the rim,his teammate is moving to offensive rebounding position and the shot-blocking defender looms. The driving player makes a quick pass to his teammate who is not expecting a pass and the ball gets fumbled away.
    This is something that is not attributed to the shot-blocker,yet w/out his presence it would have never happened.(And the reverse of late inside pass to teammate leading to a basket demonstrates there is no simple answer,just trade0offs that have to be taken into consideration.)

    I’ve alwys held that having a shot-blocker on the team has one benefit rarely mentioned. Cue AI…Practice? You’re talkin’ about Practice?
    Going against one in practice gets teammates accustomed to dealing w/one. Players learn to make their moves quicker,more forcefully. Bigs get used to idea of late inside passes and to go quick once they have the ball. They learn that getting their shot rejected may get some razzing,but it’s not the end of the world,esp when they see everybody else get rejected. They learn,they adapt and get better.

    A suggestion on following up your excellent work. Major time-killer,but finding out whether teams shoot less inside shots on elite shot-blockers than against teams w/out shot blockers and overall shooting % on games against shot-blockers/teams w/high shot-blocking rates vs other games would be very interesting.

  • ben heller

    I would argue that Gasol/Bynum, Duncan/Robinson, and Garnett/Perkins were/are all elite shot blockers (in their respective primes). I think coaching has a lot to do with where you force the opposition to take shots, so yes, players have to be both elite and in the right system to be able to put up big per-game block numbers (which is why many people prefer block rate). A lot of blocks come from help defense, so having a poor supporting cast on the perimeter will also increase the opportunities for blocks.

    About Dwight – their offense is 4-out, 1-in, but defensively, they generally have to match up with the opponent’s offensive scheme. For example, playing against Okur would draw Dwight away from the basket, diminishing his presence and making it easier for Deron to drive.

  • Lpkilla7

    Patrick Patterson can block shots big time. He was a beast at KENTUCKY regarding post defense.

  • PackJane

    Ill swat Patterson’s shot any day! He is not ready for the NBA pace or complexity..not yet

  • Ces319

    I question the conclusion that Jordan Hill should be on the court more solely by reason of his shot blocking. I think it would more appropriate to measure the impact Jordan Hill has directly on the team’s interior defense by examining opponent’s fg% at the rim when Hill is in the game and his foul rate in the paint. Blocked shots are a mean, not an end. If Hill is making mental mistakes by either fouling or being out of position and giving up high percentage shots, he might have a detrimental impact to the team’s ability to defend the rim nothwithstanding his exceptional athleticism and shotblocking prowess.

    On the other hand, as evidenced last night against Phoenix, Adelman seems willing to go with the youth movement , and I agree that given the Rockets’ current struggles, it couldn’t hurt to have a big out there that can actually secure a rebound. I’m just not so sure about his defense…

  • Easy

    Ben, great analysis. But you did not examine one element that you pointed out in the opening paragraphs: fouls. Does shot-blocking correlate with fouls committed. If it does, how does the added free throws by the opponents affect the impact of shot-blocking?

    IMO, wins vs block rate might not mean much. There are so many variables in that contribute to winning.

  • Roxfan

    We need to trade for a legit shot blocking center. We should trade with Orl for Gortat and give them Hill.

  • Roxfan

    Also, Yao should come off the bench. That way he won’t have to worry about minute restrictions. When he is on the floor, he will go up against back up centers and will be the focus of the team offense, thus maximizing his use.

  • ben heller

    Good point about fouls. I haven’t looked into it but it could go either way – every time you foul you don’t get credit for the block, so every block recorded is also a foul not recorded. On the other hand, more blocks could signify more opportunities for blocks, which would lead to more fouls. May be worth examining.

    Yes, I put up blocks to wins for that very reason – to hedge my prior statements.

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