The MIT Sloan Sports Analytics Conference just finished this past weekend. The annual affair is the league's chance for execs, agents, media, and academics to all get together and discuss the state of analytics in sports. It also is an annual sign post to track progress toward a better understanding of the game and our ability to quantify it.

This year, Kirk Goldsberry and company shared the award for best research paper. They found a way to use Sport VU tracking data to assign defensive assignments. This allows them to quantify the performance of individual defenders in exciting new ways. Quite the honor, the award is not only a statement on the quality of their work but also highlights how desperate people are for quality defensive statistics. While our offensive understanding has grown leaps and bounds the last few years, defensive metrics remain the largest gap in our statistical repertoire. For those reasons, the eye test, while always a valuable and necessary part of any analysis, is even more relevant to defensive evaluations.

We got our first opportunity to watch Arron Afflalo play defense in the Blazers' system this past week. While we can't look at every defensive possession he was a part of (he was involved in thirty plays against San Antonio alone), here are ten possessions that show his strengths and weaknesses. Keep in mind, this is only one game and it was against San Antonio, one of the most fundamentally sound offenses in the league.

Afflalo’s stance is good and low with a slight angle to force Manu Ginobili towards the baseline. Initially, he gives Manu plenty of cushion but then pressures, tracking the ball with his hands and making passes more difficult. This is critical because of what’s happening on the other side of the floor.

The Spurs ran Marco Belinelli off of a staggered screen and he gets a step on Batum curling into the paint. If no one helps, it’s an easy pass to Belinelli for a layup. Luckily, Chris Kaman and Steve Blake recognize the situation and take a step into the lane. That, in combination with Afflalo’s active hands, dissuades Ginobili from even trying the pass.

"Active hands" is a common compliment for a defender while its second cousin, "reaching", carries a negative connotation. The key difference is whether or not a defender stays centered as his hands go after the ball. If a defender reaches too far, those extra couple inches will force him to lean, upsetting his balance slightly. NBA caliber players recognize these subtle shifts, dribbling in the opposite direction and making the defender look silly.

In this play, Afflalo flirts with that fine line separating "active hands" and "reaching". It looks like he stands up just a titch and does a little hop reaching for the ball. Ginobili chooses that exact moment to dart around the screen and Afflalo is a split second behind. Normally, the Blazers try to force the ball away from the screen on all side pick and rolls but Afflalo lets Ginobili get to the middle of the floor. He should have angled his feet more drastically towards the sideline. The fact that he didn't makes it seem like he didn’t know a pick was coming and he runs smack into the middle of Splitter’s chest.

After the offensive rebound, Afflalo defends another side pick and roll. He seems caught off guard a second time and is especially jumpy as Ginobili starts his drive. You can see him trying to prevent Ginobili from getting to the middle but his footwork isn’t clean. He’s also turning his head a lot trying to figure out where Splitter is. This was one of his first plays of the game on a relatively new team so hopefully this will improve as he gets more comfortable. He certainly seemed to settle down on the defensive end as the game continued.

But not a great start.

He does a slightly better job defending the next side pick and roll a few minutes later. Boris Diaw sets the screen towards the baseline so the offense is already going in the direction Afflalo wants them to. He hits his lead shoulder into Diaw and then sort of curls around recovering to his man. It works ok on this play but he seems to get that lead shoulder caught on screens a lot. I’m a much bigger fan of guys stepping up, getting their lead shoulder around the big man and then trailing the play, staying on the ball handler's hip. This allows a defender to bother the guard from behind making it more difficult to change direction or hit a jumper. Cory Joseph didn't do much on this play but he had a lot of space. More talented point guards will turn that space into easy shots.

In this clip, Afflalo is guarding Danny Green as Kawhi Leonard drives down the right side. He takes a half step to help force Leonard to give up the ball. Green is only one pass away so it’s important not to help too much. Afflalo plays it perfectly, staying close enough so he can recover and prevent the corner three after Leonard makes the pass.

As the ball swings, Afflalo sets up at the "nail". Next time you go to a gym, see if there’s a nail in the middle of the free throw line. Most courts have them and defenses use it as a marker, just like blocking in a theater production. When an offensive player is at the top of the key without the ball, his defender should be standing on the nail, exactly where Afflalo is. Getting to the nail and then back to your man is exhausting over the course of a game and lots of players stop a foot or two short. Those extra couple feet can be enough for good players to get to the rim so this is an important detail.

After Batum doubles Kawhi in the post, Afflalo has the unenviable task of guarding both Green and Tony Parker. Players do this by "zoning up". That means they split the difference between the two shooters and are ready to run to whoever gets the ball. You can see Afflalo focus on Leonard, hopping up and down and ready to explode to whoever he passes to. I’m not a huge fan of the hopping. It takes Afflalo a beat to collect himself before he sprints to contest the shot. Arron seems to have a habit of doing this but he does a good job contesting given the position he was in.

Afflalo doesn’t do much here but I chose to include it because it illustrates an important skill - defending cutters. This is critical for Arron because wings are typically the most active cutting to the rim.

The key is to beat the cutter to the spot. If you simply stay even, the offensive player can catch the ball one step or one dribble away from the rim. That's not a lot of time for help defenders to react and it leaves you challenging the shot at the rim one-on-one. Batum can get away with doing that because of his length but there's no way Afflalo can be successful in those situations. Arron has to prevent that situation from ever occurring in the first place.

Notice how Ginobili begins to dart to the rim as soon as he sees Diaw holding the ball along the perimeter. Afflalo takes a step into the lane cutting him off and putting his forearm right in Ginobili's chest. This forces Manu to abandon the maneuver and the Spurs' offense stagnates, forcing Diaw into a tough jumper.

This is a simple high pick and roll and the Blazers defend it beautifully. Portland's scheme has very specific rules for this situation. Batum’s job is to force Kawhi to go away from the screen. Kaman’s job is drop, containing penetration. Afflalo’s job is to bump the rolling big man preventing a pass for an easy dunk. While doing this, he has to stay ready to dart back to his original man, Ginobili, if the offense kicks the ball out.

You can see each guy prepare for their responsibilities at the same time. Half the battle on defense is being in the right position before anything happens and it's critical defenders make these preparations simultaneously. If they don't, good offenses will attack the imbalances before the defense can recover. Notice how Batum angles his feet as Kaman slides in front of Kawhi and Afflalo steps into the lane all at the same time. When people talk about defenses "being on a string", that's what they mean. Once those preparations are complete, each guy follows through with his assignment forcing Kawhi into a tough runner.

This should basically never happen.

It’s tough to tell exactly where he makes a mistake. It looks like three Spurs start in a group, then Green takes a step back creating a gap between himself and Afflalo. The other two Spurs step into the gap and screen Afflalo. He gets caught up on both and Green has all day to line up a three ball, corner pocket. There’s not much to correct technically on this play, Afflalo just needed to do a better job staying connected to his man and being prepared to react quickly.

Afflalo does a good job handling the down screen. Notice how he gets his lead shoulder over and around Diaw staying on Belinelli's hip. Marco has plenty of space in front of Meyers Leonard to hit a jumper but he can't because Afflalo would just block it from behind.

In a fairly rare occurrence, Wesley Matthews pretty much blows this entire play. He loses Green on the rebound and then follows it up with a lazy close out, swiping at the ball as Green waltzes by. Kaman and Leonard do a great job recognizing the breakdown and leave their men to help. Afflalo should "help the helper" by pinching into the paint and taking away the pass to Splitter. Unfortunately, he loses track of the play after the offensive rebounded and has his back turned to the ball. That's a big no-no. They’re lucky that Kaman gets his hand on the dump pass otherwise Splitter gets a layup. Leonard and Matthews cap off the play by screwing up a switch and leaving Green wide open on the perimeter.

The Blazers typically switch all guard-wing pick and rolls and it looks like Afflalo just forgets. A certain number of these plays can be expected as Arron learns the new scheme but dang, the results sure are bad.

Luckily, AAA looks like a quick study. This is just a few possessions later when the Spurs run the same play.

Now that’s some defense! You can see Afflalo prepare for the switch, positioning himself on Green’s outside shoulder. He falls for Patty Mills’ fake spin and takes a step towards the sideline. With that step, he’s lower on the court and it would be easier to go under the screen. That would be a really bad idea given the quality of Patty's pull-up jumper. Instead, Afflalo hustles to get over the screen. Kaman takes away the drive and Patty is forced to abort and try it a second time. The result is exactly the same and Patty takes a tough, contested mid-range jumper. That's a shot the Blazers will live with every time.

This is a well designed play. The Spurs start by having Green set a baseline screen on Kawhi. This forces Afflalo and Batum to decide if they’re gonna switch and then stay out of each others way if they don't. They have to do this quickly because the Spurs immediately run Green around a Duncan down screen. If Afflalo loses even a half step communicating with Batum he's out of position for his next responsibility. Not easy.

Duncan is one of (if not the) best screeners in the game. Afflalo is right on Green's hip to start and then only loses about half a step getting around the big man. That's about as well as you can do but it still sets Afflalo up for a challenging close out.

Look at how Afflalo's feet actually touch the three point line making sure Green won't get the shot off. He then keeps his weight back ready to move his feet as Green drives. Wesley Matthews gives him a little help but this is still impressive. I mean, Dany doesn’t even get within 14 feet of the basket before coughing up a bad turnover.

How good of a defender is Arron Afflalo? We're all still figuring it out but these ten plays start to form a snap shot. It's probably fair to say the results were mixed, perhaps a little more good than bad. The most encouraging thing to note is that many of his mistakes can be traced to a lack of comfort or communication with his new teammates. That should naturally improve as he gets a few more games under his belt so this might be one of the worst defensive performances we'll see from him. When you think about it like that, AAA might be just as reliable as his nickname.