Let's look at the FG decision more closely. I won't use the WP model, but instead apply some math and logic. There were three options for Alabama:
2. Hail Mary
3. Attempt the FG
Let's make some assumptions. First, OT is a 50/50 proposition. Alabama was favored in this game, but Auburn was playing strong. Plus, OT is a bit of a dice roll to begin with. Second, Hail Marys (Maries, Mary's?) from that range are probably no more successful in college than they are in the pros, which is around 5%. Lastly, for the sake of the argument, let's say there is zero chance of a defensive TD return on the Hail Mary.
We don't really know the probability of a successful FG attempt or the probability of a successful return or block & return from a range like that, especially in college ball from a kicker without many attempts. But let's set that aside for a moment.
Kneeling would be worth 0.50 WP.
A Hail Mary would be worth:
0.05 * 1.0 + (1-0.05) * 0.50 = 0.525 WP
Now let's ask: What Field goal probability (FG) and TD return probability (R) would we need for the long FG attempt to make sense compared to the Hail Mary? We need to solve for the break-even FG% and Return% which gives us a WP equivalent to 0.525.
A good FG is worth a WP of 1.0. A miss and a return are worth 0.0. A miss and no return are worth .50 WP.
We get an equation for Alabama's WP for a field goal attempt like the following:
FG * 1.0 + (1-FG)(1-R)(.5) = .525
FG + (1-FG)(1-R)(.5) = .525
This equation produces a hyperbolic curve on a 2-dimensional plane as plotted below, where the x-axis is R (the probability of a return TD) and the y-axis is FG (the probability of a successful field goal). We can ignore the negative quadrants and only worry about the space between 0,0 and 1,1. Remember the line is the break-even, so above it the FG decision was smart, and below it the decision was not so smart.
To wrap our heads around this, let's look at an example. If we posit the chance of making the FG is 40%, the chance of a return, given a miss, would need to be less than 58% for the FG to make sense. And if we assume the chance of making the FG is 20%, the attempt would be worthwhile as long as the chance of a return is less than 19%, as shown below.
We can also look at things from the other direction. Suppose that given a miss, Auburn would return the ball for a TD 100% of the time. Alabama would need a 52.5% chance at the FG to make its attempt worthwhile. This makes intuitive sense because it's the same as the WP for the Hail Mary. This is one way of saying that the higher the FG probability, the less the chance of a return even matters.
The question becomes, which side of the curve are we on? Above the curve, the FG attempt makes sense. Below it, the attempt is too risky. To be honest, at the time I thought this was a slam-dunk good decision. But now I'm not so sure. The pros hit 57-yd attempts about 20% of the time, so that's a solid upper bound on the FG chance for Alabama. If the FG probability is 15%, the chance of return can be no more than 10%. If the FG probability is 10%, the chance of return can be no more than 6%.
We can also test how sensitive the answer is to our assumptions. For example, if we say there is no chance for the Hail Mary and that being the stronger team, Alabama's chance in OT was 55% instead of 50%, we get different answers. Under these assumptions, if we posit a 10% FG chance, the chance of a return can be no greater than 9%. And if we assume an 80% chance for Alabama in OT, the chance of return can be no greater than 3%.
One last example: If we keep the Hail Mary at 5% and set the OT chance for Alabama at 55%, for a 10% FG chance, the maximum return chance would be 4%.
My gut tells me the play was pretty close to the FG=10% / Return=6% point. The Alabama kicker maybe had about half the chance of a pro, and the chance of return was significant because of the kick's long range and Alabama's personnel. If my gut is right, we're on the borderline depending on the assumptions.
One thing this exercise shows is that all the media analysis of the decision is hot air. This is complicated stuff, relying on many variables without much in the way of empirical stats to go on. None of the opinions are based on a serious analysis or comparison of relevant past events. I heard one sports writer on the radio today say it was a bad decision because "they run those out in the CFL all the time." Ok. Define all the time. And tell me what the FG probability needs to be to trump all the time.
I don't expect people to do math like this, but let's at least spell out what the considerations are and admit how complicated it is.