Sunday, May 27, 2012

Early game intentional fouls

Stipulated that I am no student of the game, but...I think fouling in basketball to avoid a near-certain score is often a bad idea. Especially early in the game.

In last night's game 7 Celtics vs Sixers, Rajon Rondo committed a foul on the offensive player who had a pretty open path to the basket, early in the first quarter.  By late first quarter, he found himself benched to avoid foul trouble[1]. Then later in the game, he again was flirting with foul trouble and spent some extra time sitting down.

Rondo is a key starter on the Celtics. Losing his services is a big deal. He traded an important early foul to save, on average, about 0.5 pts. Seems like a bad deal to me.

How does the math on that work? Here's ordinary field goal is worth 2 points. NBA players shoot 75% on average, meaning the "expected value" of a trip to the line is 1.5 pts. 2.0 minus 1.5 = 0.5. Seems like a pretty poor return to me, and that is the best-case. Most significantly, it doesn't quantify the risk of putting the opposition into the bonus earlier.[2]

[1] Whether you should bench a key player for being in foul trouble, so readily, is the subject for another blog post.

[2] It also assumes a 100% chance the offensive player would have scored. Even with breakaway dunks, you do see a few misses. And this wasn't a breakaway--it was just an open lane to the basket. I would guesstimate an 85-90% chance it would have been converted.

1 comment:

  1. Very interesting thought. There is a lot of research about end game foul or not, but little talk about early game fouls. I tend to agree with you, certainly with a star like Rondo. The only possible exception would be early in a series to "send a message". But that motive is questionable and certainly hard to measure the effectiveness.