April 18, 2014

Dissecting Third Downs

One of the biggest improvements in the Clemson offense in the Chad Morris era has been third downs. The Tigers currently reside in 4th place in the NCAA rankings converting 52.13% of third down opportunities, up from 39.27% (and a 67th ranking) in the last year of Billy Napier calling plays.

It’s really quite remarkable. Everything being equal Clemson has a better chance than not of converting a given third down.

The problem is, of course, everything is not equal and the shorter the distance to go on third down, the better chance a team has of converting as shown in the chart below.


2012 TD Detail

We often hear announcers talk about getting to a “manageable third down” when its second and 14 or so, theory being that instead of trying a low percentage play that might gain all 14 yards needed for a first down an offense should attempt to gain half of the yards (more or less) on second down and leave themselves with a 3rd and 7 (or so) which would increase the likelihood of converting on third down. Basically, the odds of converting two shorter plays are better than attempting to convert one long play. This led me to get curious about the averages on every third down attempt (including goal to go situations) and the results are below. 2012 TD By Distance

The first two are not surprising. One would expect the highest conversion rate when the distance needed is smallest and the second highest rate when the needed distance is the next smallest. Things get a bit weird after that, when we see a huge dip when the distance to go increases from 2 to 3 and another drop from 3 to 4, after which the conversion rate goes back up in a fairly predictable pattern until 10 yards to go.

However, the 2 to 3 dip intrigued me. What happened? What is it about that extra 36 inches that caused the conversion rate to drop like a rock? The data below appears to show a shift in philosophy from running to passing when the distance changes from 2 to 3 yards. I first noticed this tendency last year in year 1 of the Morris regime. 2012 TD Comparison

The longer distance leads to a predictable decrease in success rates for rushing attempts, but the 36% conversion rate on passes is also interesting to me. Two of those failed passes were drops (Brandon Ford against Auburn and Sammy Watkins against N.C. State). For our purposes here it really doesn’t matter why they failed, just that they failed.

While the decrease in conversion on rushes was predictable, I was intrigued by trends that may become apparent by breaking down the rushes by player and I wasn’t disappointed. I think we all knew that the Tigers relied on Tajh Boyd in short yardage, but these two charts show that not only do they rely on Boyd on 3rd and 4th and 1 as previously written here, but the same is true on 3rd and 2 or 3, despite a higher success rate for running backs in similar situations. 2012 Third Down 2 _ 3 By Player

Does anyone else find it strange that the star running back, one of the top rushers in school history, carried the ball 2 (of a possible 13) times on third and 2? Or 4 of a possible 21 times on third and 2 and third and 3?

You’re probably thinking what I was – McDowell’s chances came in blowout time as did Howard’s, Stoudt’s and Davidson’s. That is true – for the most part. Two of McDowell’s carries came in blow out time (as did the carries from the other players). Still, that means Ellington carried the ball 4 of 16 times (25%) on 3rd and 2 or 3 when the game was in doubt. Boyd carried the ball 62.5% of the time in these situations.

There could be obvious reasons for this disparity. Boyd has improved as a runner and he’s closer to the line of scrimmage, minimizing the chance for a negative play. There’s less chance of a bad exchange and turnover. Perhaps Boyd is changing the play at the line depending on the alignment of the defense. 

On the other hand we aren’t talking about 3rd and 1 (or inches). We’re talking about 3rd and 2 and 3rd and 3. There’s a risk that the quarterback gets stuffed by a lineman that a running back could potentially avoid and the running back is moving forward at the snap while the quarterback is stationary.

This led me to wonder about how often (as a percentage of total carries) Ellington and Boyd carried the ball on third down. Naturally, one would think that Ellington’s percentage would go down from first, to second to third to fourth down. And already knowing that Boyd carried the ball a great deal on third down, I suspected his number would be relatively high. I had no idea of the disparity. Boyd carries the ball 4 times as much (as a percentage of carries) on third down as Ellington. The question is why? BoydEllington_ThirdDownRushes
My guess is Morris calls more plays for Boyd and Boyd changes a few based on the defense. If we are talking read option here, there hasn’t been much optioning.  One would think the defense would eventually force Boyd to give the ball up, which leads me to believe that most of these are not options, but designed runs (my eyes tell me that, too). 

We’ll never know how much of each of these has caused the diparity in numbers, but a couple of things are obvious to the average observer – Morris is more comfortable with Boyd carrying the ball in these situations and Boyd carries the ball more on third and 2 or 3 than everyone else combined (when game is in doubt), regardless of field position and game situation.

With the overall success on third downs, it’s hard to pick nits here. After all, as I pointed out earlier the Tigers are 4th of 120 teams in third down conversions. My intent here was not to criticize the play calling or suggest I know more than Morris about what call to make on third and 3 or what player to lean on when its third and 2 – obviously I don’t.

My intent is to point out what is likely to happen in the future given what has happened in similar situations in the past.

Other interesting discoveries:
• Clemson has run 5 plays from the opponents 3 on third and goal. 3 Boyd runs and 2 Boyd passes.
• No one else has carried the ball on 3rd and goal from the 3.
• Only 1 of the above 5 plays was successful – Boyd scored on a 3 yard run against South Carolina on 3rd and goal from the 3.

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