Chip Kelly and Two Point Conversions (hypothesis formulation)

UPDATE: The following is a case for occasionally attempting 2 pt conversions earlier in the game (when current coaches don’t typically try them), NOT going for two every time.  Should have made that clearer.

There’s an article up on Bleacher Report that talks about the possibility of Chip Kelly attempting 2-point conversions more often:

It’s interesting because it indirectly highlights how one of the biggest weaknesses (assumed) to Chip Kelly’s candidacy might also be one of the biggest strengths.  Kelly’s lack of NFL experience is presumed to increase the risk that he won’t be successful as a coach, however, all Eagles fans should hope that this also has the side effect of freeing Kelly from some prevailing NFL wisdom.  Specifically, I’m hoping Kelly takes a much more aggressive approach to both 2-point conversions.

As most fans know, the 2-point conversion gives the offense the ball at the 2-yard line, with one play to get in the end zone.  Much has been written about the optimal strategy regarding 2-point tries, with mixed opinions.

However, among NFL coaches, there seems to be a general consensus that you should NOT go for two unless it is absolutely necessary.  Assuming NFL coaches have actually looked at the statistics, we are led to believe that they are deferring to the historical success rate, which is in the 47%-48% range depending on which plays the data compilers include (botched kicks for instance).  A 48% success rate means the expected value of an extra point is higher, and therefore the correct play.

So why do I want Kelly to go for it more often?  I believe that the following three aspects, when aggregated, will lead to a higher than 50% success rate, meaning the expected value for the 2-point conversion will be higher than an extra point.

– If we assume that the league-wide success rate is 47-48%, then obviously some teams have better conversion rates.  I have not pulled the statistics (unfortunately they are not as readily available as most other measures), but I think it’s reasonable to suggest that a team with an above-average offense can expect to have an above-average conversion rate as well.  (If Chip Kelly does not put together a better-than-average offense, he will be a huge disappointment.)

– I’m also hypothesizing that the element of surprise via the no-huddle offense will itself add to the conversion success rate.  NFL defenses have been conditioned to leave the field after allowing a TD.  It’s a fairly small jump to assume that an NFL team using a hurry-up offense to attempt 2-point conversion, especially in the first half, will catch the defense off-guard.  The associated confusion/lack of defensive focus will presumably add to the likelihood of offensive success.  (Yes, if the Eagles always went for two, they would lose this element of the strategy.  That’s why its best implemented only occasionally.)

– Lastly, currently teams do not devote a significant amount of practice time towards the 2-point conversion.  Obviously, considering the rarity with which most teams attempt the play, devoting practice time to it likely isn’t worth the time spent.  However, if a team decided to implement the 2-point play more often, then it would therefore make sense to practice the 2-pt playbook more often.  Does anyone disagree that practicing the plays more often would make them more effective?


I apologize for the lack of data here, but we’re dealing largely with a theory that hasn’t been tested in the NFL.  While the above analysis may seem a bit disjointed, the overall question is as follows:

Would the 3 factors mentioned above (strong offense, surprised defense, more practice) add more than 2%-3% to the overall 2 pt. conversion success rate?

If you believe the answer is yes, then hope that Chip Kelly’s ego is (as I suspect) big enough to give him the confidence to move strongly against prevailing NFL wisdom.

P.S. Unfortunately, the most easily predicted aspect of this plan is commentator reaction.  Even if it is statistically the right play, you can bet every announcer will talk about how “bold” and “risky” the decision is, as well as how stupid it is every time it doesn’t work.


3 thoughts on “Chip Kelly and Two Point Conversions (hypothesis formulation)

  1. While I understand your points, I just cannot agree with it. You mention in your first point that above average offenses will have higher conversions rates. That’s fine. However, you neglect to consider that above-average defenses are better at defending 2-point conversions and teams playing these defenses will consequently have lower conversion rates.

    Further, while it’s true that practicing 2-point conversions would increase the success rate of 2-point conversations, this would come at a cost: using that practice time to be better at something else. The only way your third point is logical is if the benefit received from practicing 2-point conversations is more beneficial than the benefit received from practicing something else. Given how theoretical this is, I doubt either one of us could say for certain.

    Finally, even assuming you are correct that the expected value for the 2-point conversion is higher than going with a 1-point conversion (which I disagree with) I would have serious reservations with such an approach because of how streaky repeatedly going for 2-point conversions would be. Let’s say you’re right and the success rate is 52%. That means 52% of the time you’re getting two points. However, it also means that 48% of the time you are getting NO points. If that 48% happens multiple times in the same game, you’re giving the other team an edge. I guess what I’m trying to say in this paragraph is that I’d rather have a consistent expected value than a streaky but ever so slightly (and I mean ever so slightly) higher expected value. I can see how you’d disagree with me on this point though. (However, if you’re only saying to do 2-point conversions occasionally because of a surprise factor involved from a surprise 2-point conversion, then, assuming the surprise factor gives a significant advantage, I’d see your argument and my final paragraph here is moot. You might be implying in your second bullet point that this is the whole point of this blog post but I’m not certain as occasional use of 2-point conversions is only mentioned in your second point).

    • Good stuff. First, I am indeed advocating only occasionally going for two, not doing it every time, so as to keep the surprise element. I would not, for example, encourage the team to go for it after missing an earlier attempt in order to “catch up” to what they should have scored. As you mentioned, missing multiple times in a game would be pretty harmful.

      Regarding your first point, obviously a good defense will be better at stopping 2 pt. conversions than a bad one. However, that’s already factored into the overall success rate. So offenses of all skill levels have a 48% success rate against defenses of all skill levels. All we are doing is assuming we would be in the top section of those offenses, which would presumably carry a higher success rate. However, the strategy would take opposing defense into account, so you wouldn’t go for 2 as often against top defenses as you would against weak ones. This may be particularly helpful against teams with an unbalanced Offense/defense talent level.

      I did consider your second point regarding the practice time, and you’re right that neither of us can know for sure. My thinking was that practicing for a two point conversion would also benefit the team for other short-yardage conversions and would therefore not be at the complete expense of other areas of the game. It probably depends on each coaches’ practice style.

      I’d also encourage everyone to consider the effect of the 2 pt conversion use on the opposing team. For instance, going up by 8 points throws a wrench into the other team’s strategy. If they score a TD do they go for 2? This adds additional complexity to the other team’s game-plan that the likely haven’t prepared too much for. As I mentioned a few times this season, any time you can give the other team more things to think about, it increases the chances they make the wrong decision.

      Thanks for the comment. It’s helpful when people push back. Means I have to put more effort into refining the idea, making it better.

      • Your response cleared up most of my concerns then. Yeah I’d love to see a coach go for two more often. I thought you were advocating for liberal use of 2-point conversions, but I’m on board with using them occasionally and strategically.

        Sure. This is a great blog and I appreciate your posts :-).

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