To borrow a term from local blogger Flash, let's take a look at a few numbers of players that Al Jefferson is often cited as having trouble with at the defensive end of the court.  The reason for doing this is to build on my post from earlier in the week that talked about playing Al at the 5. 

Before I continue, let me just point out the absurdity of arguing that Jefferson is more suited for the 4 because of his PER positional court time numbers.  By the same logic exhibited in the post at the above link, New Orleans fans should be clammoring for Tyson Chandler to play the 4.  His sample size is essentially the same as Big Al's and he has about the same differential between PER as does everybody's favorite T-Wolf.  Somehow, the Hornets survive with Chandler playing at his "unnatural" position. 

Let's continue to take a look at the numbers of these players:

One of the things that jumps out with these numbers is the off/def +/- numbers of Jefferson compared to the other players.  He carries large negative numbers that would make him seem like an inferior player.  However, when you take into account that the Wolves carry a -8.5 stat as a team (compared to +6.6, +6.5, and +6.5 of the other teams), he perfoms about as well as can be expected on a 22 win team with the 27th worst offense and defense in the league. 

What you will also notice about these numbers is that Jefferson is able to get his own on a level unmatched by the other players.  Part of this has to do with the fact that 2 of these players (Amare and Chandler) play with top flight point guards who can get them the ball in a position to score inside.  What the numbers also say is that Jefferson is a more effective offensive player at the 5.  The reason for this is that when Jefferson plays at the 5, he takes more shots inside the paint: 55% of his shots are iFGs.  When he plays at the 4, only 43% of his shots are iFGs.  This is an important stat because when Jefferson shoots from the inside, he carries a 64% eFG.  When he shoots jumpers, he only nets a 37% eFG.  In other words, the man needs to be kept as close to the low block as possible.  By playing the 4 (and granted, this is with a very small sample size), Jefferson may make some defensive gains, but he does so at the expense of his greatest asset: his inside scoring ability.  I'll ask it again: How can a 22 win team ask its best player to abandon his best position? 

Hitting on this point a little more, Jefferson carried a slightly better net efficiency gain at the 5 compared to the 4.  He maintained the same point differential at the 5 as he did at the 4 but he lost a bit with rebounding and FTAs.  What does this suggest?  If you look at his overall efficiency marks, as well as the team's, it suggests that Al plays better man on man defense at the 5 but it may come at the expense of team d.  Where this gets tricky is that his offense is so much more efficient at the 5, that he makes up for any loss in team d by an overall net gain in efficiency.  Ultimately, much of his lack of success is tied direcly to the general lack of success of his team.  Quite simply, the Wolves sucked. 

Moving forward, the best parts of Jefferson's game are geared to the offensive end of the 5: he's a dominant low post scorer who isn't that great of a jump shooter.  When he plays the 4, his game is significantly altered to the point that he takes more jumpers and less shots inside the lane.  While he gives up a lot more points/100 possessions at the 5, he also scores a lot more and he does so in a more efficient fashion.  It is unlikely that he will develop into a dominant man-on-man defender like Howard, or a dominant help defender like Chandler, but it is equally unlikely that either of these players will develop into a dominant low post scorer like Jefferson.  Should Jefferson ever be blessed with a lead guard who can get him the ball to the tune of 70-80% of what Steve Nash and Chris Paul do for Amare and Chandler, or should he ever be blessed with a second low post option that would allow him to focus on the low block, his numbers (as well as the team's) should dramatically increase.  Here's hoping that Mr. Love can give Big Al what he needs with regards to the latter. 

UPDATE: I want to highlight something I said to Wim in the comments.  Here's what I think the Jefferson 4/5 debate boils down to:

Do you try to maximize his offensive efficiency or do you try to minimize his defensive inefficiency?

That's pretty much it.  I admit there is a certain amount of semantics involved in deciding if he's better off at the 4 or the 5, but this question gets to the heart of the matter.  Do you surround him with a defensive-minded frontcourt player or with one that can insure he stays in the low block and does what he does best?