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Thursday, March 24, 2011
When fouling is good

By Henry Abbott

Fouling is bad. Very bad. You stop the clock. You give your opponents free throws. You get players into foul trouble. You get opponents into the bonus, which makes just about every offense far more effective. When your players have a lot of fouls, they play timidly. Fouling is to be avoided, just about all the time.

But there are times smart coaches do it intentionally, for instance for possession at the end of close games they're trailing.

Maybe there's another time to do that, too.

A basketball game is essentially a fixed number of possessions for each team. You don't get to know at the outset how many, but by the time of the final buzzer, both teams will have had basically the same number of attempts -- if it's a Portland game, that number will tend to be around 90. If it's the Knicks, both teams are likely to be closer to 100.

One team's possession begins after the others has ended so almost by definition, both teams will finish the game with the same number, give or take one or two.

There's a trick, though, and it's in that word "almost" in the last sentence. Possessions do alternate all game (if my team gets four straight offensive rebounds, that still counts as one single possession) except at the beginning of periods. At the beginning of the first period, the ball goes to the team that wins the tip. After that it's handed out on a set formula -- team that lost the tip gets the next two quarters, the team that won the tip gets it to start the fourth.

That creates a nifty little opportunity to have an extra possession or two. Think about this: If you have the ball at the end of every quarter, that means now and again you'll have that rarest of NBA efficiency treats: Two straight possessions. You could actually score a buzzer-beating 3 to end one quarter, and then just score again without the other team even touching the ball once. This is not just rare in other times of the game -- it's impossible.

And in the long haul, if you're averaging a possession or two more than your opponents, in a league where a typical win is by three points or so ... that matters.

Basically, that last possession of the quarter is often a free one.

So, what do you have to do to get that extra possession? There are various strategies, including a whole rich long-term stats and coaches debate about how to manage the two-for-one. (Most feel you should shoot with around 30-45 seconds left. Then your opponents will use some clock and likely leave you inbounding with 24 or fewer seconds and an opportunity for the last shot of the quarter.)

But in cases where the standard clock management strategies fail, and your opponent is inbounding with 20 seconds left in the quarter, well, you know how you can get that thing back, right?

You can foul. They'll get two free throws. You'll get all the downsides of fouling.

But it's all a trade, for a free possession. A possession you just would never have otherwise.

Is it worth it? Is that a good trade?

Summon your stat geeks!

I can tell you this:
David, a commenter on the economics blog Marginal Revolution writes: "A possession is worth 1.1 points in an NBA game or so. A possession with two free throws shot by a 75 percent shooter is worth 1.5 points. If you foul, though, you get the ball back and a possession yourself. It will be a short possession, so it’s possibly not worth a full 1.1 points, but it’s not worth nothing. By my assumptions, the possession only has to be worth 0.4 points to make fouling an attractive strategy."

Here's the thing to realize: By fouling, you're not giving them 1.5 points. You're giving them those 1.5 points minus what they would have gotten otherwise. If you don't foul them, in other words, they're still going to score some of the time -- and they might score a 3. Maybe, playing against the clock, they'd average quite a bit less than a typical 1.1 points per NBA possession. But still, let's say they're going to score 0.8 points per possession. You're going to hand then 0.7 points with your foul, an amount even the lamest offense can make up with a single possession.