Should Nick Saban have gone for it on 4th down? A LSU, Alabama (p)review.

Alabama marched into LSU territory plenty of times. In their early November showdown, Alabama got to the LSU 27 and 33 yard line on their first two drives, only to have Cade Foster miss two field goals. The next Alabama drive stalled at the LSU 31, and this time coach Nick Saban gave Jeremy Shelley, usually their short field goal kicker, a shot from 49 yards. LSU blocked this attempt. In their epic defensive showdown, Alabama outgained LSU in total yardage (295 to 239) but ended up losing 9-6 in overtime. With all those deep penetrations into LSU territory, should Saban have gone for it on 4th down?

Here, we list the 4th down situations that confronted Saban, along with the result.

4th and 7 at LSU 27; Foster missed a 44 yard field goal attempt
4th and 20 at LSU 33; Foster missed 50 yard field goal attempt
4th and 17 at LSU 31; Shelley had 49 yard field goal attempt blocked
4th and 8 at LSU 17; Shelley made 34 yard field goal
4th and 4 at LSU 29; Foster made 46 yard field goal

So what does analytics say about 4th down decision making? Brian Burke, founder of Advanced NFL Stats, has done the most complete analysis of the subject based on the NFL. With no similar analysis of college football, we’ll look at Saban’s decisions through this work. Clearly, this is far from ideal, and we’ll address these concerns later.

Expected Points

To understand Burke’s analysis, we must first introduce the idea of expected points. For a situation, such as 1st and 10 from the offense’s 27 yard line, the expected points is the average net points for the offense on the next score. If a team gets a 1st and 10 from the 27 a million times, sometime they will score a touchdown for +7 points. Other times, the defense will hold, resulting in a field goal for the other team, or -3 net points for the offense. Perhaps, the defense even returns an interception for a touchdown (-7 points). But an average over all these scores gives a net 0.7 points for the offense. Burke arrived at 0.7 by looking at every 1st and 10 starting at the 27 from the 2000-2008 NFL seasons and averaging the next score in the game. For the expected points for a 1st down at every yard line, see this figure.

These values for expected points allow Burke to evaluate 4th down decision making. This is easiest to understand with an example, such as the 4th and 4 from the LSU 29 that Alabama faced. Alabama has a 53% chance of making a 1st down, which we’ll assume will spot the ball at the LSU 25. This is worth 3.6 expected points. In the 47% chance that Alabama doesn’t make the 1st down, we’ll assume LSU gets the ball at the 29 yard line. This is worth -0.9 expected points for Alabama. To calculate the expected points, we add the probability of each choice times the expected points for each outcome. In this case, (0.53 * 3.6) – (0.47 * 0.9) gives 1.46 expected points for Alabama.

For a field goal attempt, the average NFL kicker will convert 67% of field goal attempts from 46 yards out. This is actually worth 2.3 expected points, since we must subtract 0.7 from 3 because the kickoff gives the opponent the ball at their 27 yard line. Missing the field goal gives LSU the ball at the 29 yard line, again worth -0.9 expected points for Alabama. Performing the same analysis as before gives 1.24 expected points for kicking the field goal. Since 1.24 is less than 1.46, Alabama should have gone for it on 4th down. This analysis is summarized in this plot of line of scrimmage versus yards to go on 4th down.

Analytics says that Saban was…

Based on Brian Burke’s work on the NFL, we just showed that Nick Saban should have gone for it on 4th and 4 from the LSU 29. However, this analysis implies that Saban should NOT have gone for the 1st down on the other four 4th down situations. He made the right call to kick a field goal. In each of these four situations, his offense faced 7 or more yards to the first down. This distance presented a daunting challenge, especially against LSU’s defense.

Of course, Saban shouldn’t hitch his coaching career to this study. Many factors make it difficult to apply analytics to actual 4th down decisions. First, Burke looked at NFL games, and many quantities such as 4th down conversion rates could differ in college football. Second, Burke’s analysis averages over all teams, which doesn’t account for how a good Alabama offense (12th in our offense rankings) will match up with an exceptional LSU defense (2nd in our defense rankings behind Alabama). Lastly, the quality of the kicker has a huge impact on the analysis. From the outside, Cade Foster only attempts field goals from 40 yards or greater. While he’s only 2 of 9 this year, he banged home 7 of 9 last year. On the inside, Nick Saban probably knows best the likelihood that Foster will make a 50 yard field goal. Analytics doesn’t have all the answers and never will in a complex team sport like football.

National Championship Game Preview

However, analytics can provide useful guidelines for 4th down decision making. If you look at Burke’s 4th down decision plot, a team should almost always go for it with 2 or less yards to go. This is true as far back as the 28 yard line, the spot in which New England coach Bill Belichick famously failed to convert a 4th and 2 against Indianapolis. For Nick Saban on Monday night, he might consider going for it on 4th and 2 at the LSU 20. The Tiger’s defensive line is stout, but Alabama features Outland Trophy winner Barrett Jones on their offensive line and Heisman finalist Trent Richardson at running back. Moreover, quarterback AJ McCarron has completed almost 67% of his passes this year. Alabama has all the tools to score more than 6 points against LSU’s defense.

The Power Rank predicts LSU has a 60% chance of winning. What do the other 40% of outcomes look like? LSU excels at every position on the field except quarterback. Despite his athleticism, Jordan Jefferson has completed 59% of his passes over his career. His backup Jarrett Lee has posted a 56% completion rate over his career, although he has completed 62% of his passes this year. Lee came into the Alabama game earlier this year with an absurdly low interception rate. We forecasted that this low rate would not continue, and he threw 2 picks against Alabama. A similar performance by Jefferson on Monday night could tip the game for Alabama.

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About The Power Rank.
Can a defense force turnovers?
College football’s incredibly slow progress towards a playoff.
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