Saturday, April 3, 2010

Opponent-Adjusted Four Factors

This is something I’ve been thinking about for some time, and I finally gave it a shot yesterday.  I should point out right up front that I haven’t done any kind of testing to see if the way I’ve implemented it makes sense, nor checked to see if the adjusted numbers are more predictive than raw Four Factors data.  But I wanted to get a rough draft of the system done before today’s games are underway – I’ll test and tweak in the off season.

My method was basically to reproduce the Pomeroy ratings, except using (for example) offensive and defensive OR% instead of offensive and defensive efficiency.  I tested the method first on efficiency, just to make sure I was able to reproduce Pomeroy’s numbers.  He actually weights the numbers based on how recent the games are, and I didn’t try to mimic that, but my numbers still essentially aligned with his:


That’s the easy part; I’ve done that before.  The trickier part was deciding what value to use for home field advantage for the various factors.  Pomeroy uses 1.4% per team for each number - he adds 1.4% to the home team’s offense and visitor’s defense, and subtracts 1.4% from the home defense and visiting offense.  I don’t know where he got that number, but I was able to roughly reproduce it (1.25%) by looking at only home-and-home games from this season, finding the average overall efficiency, and the average home efficiency, and then taking the square root of the ratio between the two:

( [Ave Home Eff] / [Ave Overall Eff] ) ^ 1/2 = (103.6/101.0)^0.5 = 1.0125

Since this makes sense, and seems to reproduce Pomeroy’s HFA number, I used this method to come up with the HFA adjustments for the Four Factors:

  • eFG%: 1.007
  • TO%: 0.980
  • OR%: 1.007
  • FTR: 1.031

Once I had these, all I had to do was re-do the opponent adjustments using the Four Factors and their HFA’s, instead of the efficiency values.  Then I looked to see if the outputs passed the smell test.  I’d say they look fine; here is a comparison of the raw and adjusted Four Factors rankings for the Final Four participants (click image for larger version):


I highlighted a few of the significant changes.  For the most part, all the teams look better in all the categories, but there are a few exceptions.  Here are a few notes:

  • The only instances where the adjustment moved a team’s ranking down more than a couple spots were Butler’s eFG% and Michigan State’s FTR.
  • Duke and West Virginia’s shooting numbers are not as bad as they seem – the adjustments pull them up to basically even with Butler and MSU.
  • Michigan State’s turnover problem is as bad as it seems – especially with the adjustment improving Butler’s defensive TO%.
  • The best three offensive rebounding teams in the nation are still alive.
  • Butler doesn’t have as much of a defensive rebounding advantage as I thought.
  • The FTR adjustment for MSU is interesting – I’m wondering if that is a result of Big Ten officials “letting them play.”

Of course, now that I have these numbers, the obvious temptation is to use them to predict the Four Factors numbers for tonight’s games.  I of course gave in, but right now I have no faith whatsoever in the accuracy of these.  Just for fun, though:


Eyeballing those, it looks like Butler wins by forcing Michigan State turnovers, and Duke wins by forcing West Virginia into a poor shooting night.  Sounds about right to me.

Thursday, April 1, 2010

How They Won (Or Lost): Adjusted Efficiency by Region

The idea here is pretty simple.  I just took a team’s actual offensive and defensive efficiency for every game, and adjusted it to account for opponent ratings.  Then I averaged those adjusted efficiencies over all the games a team played.  This should not be thought of as who “deserved” to win each region, for a number of reasons (consistency, skewed numbers from blowouts, etc).  It’s merely showing you how well a team played while they were still alive.  Final Four teams are in bold.


The top three teams here have the 2nd, 3rd, and 4th best Margins in the whole bracket, behind only Duke.  It’s too bad only one of them was able to make the trip to Indy.  WVU won by playing the best defense in the whole tourney – yes, they’re even rated better than Butler. After their gimme against Morgan State, they then beat the teams that performed 4th, 5th, and best in the region. Marquette gets the “tough luck” award, as they turned in the best performance of any first-round loser.


This is either evidence of Tom Izzo’s genius, or of his insane luck, depending on which side of the fence you’re on.  I feel sorry for Tennessee, who beat Ohio State, then lost by a free throw to MSU - I can definitely see how they topped the chart.  And Michigan State wasn’t the best at anything (off/def/marg).  Georgetown and Kansas laid the biggest eggs here (obviously), both on the defensive end – congrats to Georgetown for being the only major conference team with a negative adjusted margin.  The highest rated team here would have only ranked 4th, 4th, and 5th in the other regions.


This is the only region with a team that clearly outperformed everybody else – not surprisingly, it’s also the only region where 1st-ranked team made the Final Four.  Duke’s offense has been the 3rd-best so far, behind only Cornell and Marquette.  Their defense has been 8th-best.  Villanova played worse than 5 of the 8 first-round losers in this region - including Robert Morris.  Surprisingly, though, it was their offense that didn't show up.


Syracuse and Butler were a cut above the rest statistically, and I don’t think you can really argue that Butler wasn't the best team.  It occurs to me now that perhaps Pythag would have been a better way to go than Margin – Butler would have topped this region at 0.982 to Syracuse’s 0.980.  Oh well.

Wednesday, March 31, 2010

Similarity Preview: Duke Vs. West Virginia

[NOTE: Cross posted at UFR. For more info on similarity scores and predictions, see here and here.]

Saturday’s headlining game features the offenses ranked 1st (Duke) and 12th (West Virginia) in adjusted offensive efficiency, compared with 25th (Michigan State) and 46th (Butler). So it obviously features the better shooting teams, right? Nope:


Duke and WVU made it this far not because they make the most of their opportunities, but because they get so many more opportunities than their opponents. They’re both great rebounding teams, and also come out on the plus side of the turnover balance sheet. In fact, when you add together their rebounding and scoring margins, they are the top two major conference teams in the country, in terms of creating extra chances for themselves, with both averaging over +6 in combined Reb+TO margin. Obviously they can’t both keep this up on Saturday, and whoever wins the “extra chances” battle will have a very good chance of extending their season.

Now let’s get more specific, and look at what to expect when Duke has the ball:



Duke’s not going to be able to get a lot going from inside the arc, as they’re below average in 2P% while WVU is on the plus side. And not shown here is the fact that the same is true for Block%, meaning the interior defense of Wellington Smith and John Flowers may end up playing a key role. Flowers had 3 blocks in 23 minutes against Kentucky, and I’d expect the two players to combine for at least that many against Duke.

But as indicated above, Duke’s emphasis is on using offensive rebounding and a low turnover rate to ensure they get a lot of looks at the basket – a good shooting night would just be icing on the cake. West Virginia is above average at defensive rebounding and forcing turnovers, but just barely. Here is how they fared this season against major conference teams in the top 30 in OReb%:


It’s going to be tough to beat Duke if they allow another 40% offensive rebounding night. They were able to overcome that against Kentucky by holding them to a low shooting percentage (37.3 eFG%) and forcing a lot of turnovers (22.6%). They might be able to hold Duke to similar shooting numbers, but likely won’t be able to force them into that many turnovers. Duke should be able to take care of the ball, and get a lot of first and second shot opportunities, but their best looks will be long jumpers. How efficiency they are will ultimately come down to whether they are hitting those jumpers.

You may have noticed above that West Virginia plays at a slow pace, and are wondering whether that will frustrate Duke. No, not at all – the Blue Devils have played 12 straight games at a sub-70-possession pace, and for the year they are 17-1 in games with 65 or less possessions. Shouldn’t be an issue.

Now how about when West Virginia has the ball:



This is going to read a lot like the section above, so I’ll keep it relatively short. West Virginia should also have trouble getting open first looks on offense, but Duke defends the perimeter (1st in 3P% against, 10th in fewest 3PA/FGA) better than the interior (39th in 2P%), so the Mountaineers won’t have as many open long jumpers as Duke will (nor as many as they had in the first half against Kentucky). However, WVU is even less dependent on good shooting than Duke is, as they’re even better at offensive rebounding (and because they shoot more 3’s, there are a few more rebounds for them to grab). They also get to the line slightly more, but it’s a small advantage.

So if everything holds true to form, West Virginia’s offense will look largely the same as Duke’s. They’ll turn it over a bit more, and probably shoot a bit worse (especially from long range). But they’ll draw a few more fouls, and grab a few more rebounds. The core strategy will be the same, though – throw it towards the hoop, then go and get it in the likely event that it misses.

Let’s look at the Similarity Prediction:


Vegas has the Blue Devils favored by 2.5, and Pomeroy’s numbers have them even stronger. The similarity analysis disagrees, showing that both teams have performed nearly the same in games against similar opponents – which makes perfect sense, given that both teams use the same volume-over-efficiency strategy on offense, and both rely on good FG% defense (as opposed to turnovers or rebounding) at the other end. Duke and West Virginia usually miss a lot of shots, but make up for it with excellent offensive rebounding. If one of them starts hitting their first chance shots, or if one can dominate the boards, that team will probably win. Duke is better at shooting and defending the three point line, and that advantage is what separates the two teams statistically. But given West Virginia’s first half against Kentucky, it should be clear that anything can happen in a span of 30 possessions. Duke’s perimeter advantage will likely be less important than the advantage that one of these teams gains through luck – or clutchness, or heart, or whatever you want to call it. So I feel comfortable with the similarity prediction – Duke as a slight favorite, but really anybody’s game.

Tuesday, March 30, 2010

Similarity Preview: Michigan State Vs. Butler

[NOTE: Cross posted at UFR.  Also, for background on the similarity scores and predictions, check out here and here.]

The early Final Four game on Saturday pits Michigan State against Butler. To get there, the Spartans squeaked by a parade of low seeds, winning by a total of 13 points against teams seeded #12, #4, #9, and #6. Butler, on the other hand, beat #2 Kansas State in the regional final by 7 points – more than Michigan State’s combined margins for their games against New Mexico State (3), Maryland (2), and Tennessee (1) – and led #1 Syracuse by double digits before eventually winning by 4. This is all a long way of saying that in the games I watched, Butler won by outplaying their opponents, while MSU won by out-lucking them. But what’s done is done, and the way a team advanced to Indy isn’t going to affect this weekend’s final score. The only thing that matters is what goes down on the hardwood. Let’s take a look at what to expect when Michigan State has the ball.


Despite losing Goran Suton, and having no regulars taller than 6’8”, Michigan State’s 2010 offense is a near clone of the 2009 version. OK, not that weird, right? Well, how about this:


Despite never having Goran Suton in the first place, Butler’s 2010 defense is also a clone of 2009 Michigan State. If ever there were a game perfectly set up to let Tom Izzo demonstrate his supposed March coaching genius, this is it. He’s facing a Butler team that’s drawing (justified) raves for its tremendous tourney defense, having manhandled two offenses that are significantly more efficient than MSU. His team’s leader in minutes, points, and assists is out of commission, and other significant players are nursing injuries. His opponent will be playing a mere 6 miles from their home gym. But the basketball gods have handed him an advantage to exploit – this fabulous defense that he’s up against is a whole lot like the one he happened to coach last year, and you’re fooling yourself if you don’t think a great coach like Izzo wouldn’t know how to best attack his own defense. How much is that style-familiarity worth? Beats me.

Monday, March 29, 2010

Prediction System Bracket Challenge: Final Four Update

Ha, check it out!


Using the default ESPN scoring, the battle for 1st place is down to (if WVU beats Duke), Yet Another Basketball Blog (if Duke wins the whole thing), and myself (if Duke loses in the title game).  As I mentioned in the intro post, I think the default scoring weights the last few rounds too heavily.  Here are the standings if you go to the opposite extreme, and give only 1 point per game, no matter what round:

Looks like I want to see a Butler over Duke final – not coincidentally, that’s also what I’m rooting for in my real-life pools.  Sometimes I trust the numbers too much…

I’ll of course be back next week with a final standings update.

Something’s Gotta Give: Extra Chances

I noted in a pre-tourney post that Duke makes up for their poor interior shooting by corralling 40% of their misses, which gives them more cracks at the basket.  That’s really only part of the larger story, which is that this Blue Devils team is one of the best in the country at getting themselves more scoring chances than their opponents.  Let me explain what I mean.

Given the national averages listed on Pomeroy’s site for TO% (20%), 3PA/FGA (33%), 3P% (34%), 2P% (48%), OReb% (33%), and FTA/FGA (38%), I estimate that about 2/3 of all possessions are simple one-chance affairs, where a team gets exactly one shot attempt (or one trip to the free throw line).  The actual number’s not important – the point is that one-and-done is the natural state of things.

There are two things a team can do that will disrupt this natural state – grabbing offensive rebounds and forcing turnovers.  We can count how many times a team does these things, and how many times they let their opponents do them, and the difference will represent the “extra chances” that a team has over the course of the game.

Using Duke as an example (numbers pulled from
ExtraChances/G = (OR/G – OppOR/G) + (OppTO/G – TO/G)
ExtraChances/G = (12.9 – 9.7) + (14.2 – 10.8) = 6.6
This can be further adjusted for pace:
EC/100 = 100 * (ExtraChances/G) / (Poss/G)
For the teams in the Final Four, this doesn’t make much difference, so I’ll be ignoring pace for now. (Plus, you could argue that a higher pace for these teams is a good thing, and we don’t want to toss that info.)  I pulled the stats for every 2010 team and found their ExtraChances/G.  Here’s a Google Spreadsheet that shows them all – I’ve highlighted the Final Four teams in blue:

Saturday’s main event will be a battle between the best two major conference teams in the country, in terms of creating extra chances for themselves.  These teams win by exploiting volume, as opposed to efficiency, and obviously they can’t both come out ahead.  If one of them does, there’s your likely winner.