Since I’m currently in the mode of defending two-point conversion attempts, I wanted to write a quick post about why the Giants decision to go for two during last night’s 23-20 loss to the Falcons was the correct call despite the outcry from ESPN’s broadcasters in the booth. If Joe Tessitore, Jason Witten, and Booger McFarland had been paying attention to the end of the Eagles-Vikings game two weeks ago, they would have already seen this and known why teams are likely going to be doing this a lot moving forward.
As most of you know, I’m a big proponent of using analytics in football. Numbers don’t score touchdowns or make blocks, but they can help you increase your odds of winning if you use them to help guide your decision making. Football is different than most other sports because of the way scoring works. You don’t just score in 1’s like baseball, soccer, or hockey, you score in 6’s, 3’s, 2’s, and 1’s.
Understanding the odds behind certain events and how those odds effect potential game outcomes is what analytics is all about. It’s the same as playing “by the book” in blackjack. Hitting on a 16 when the dealer is showing a 7 may feel risky and you’re often going to bust, but statistically that maximizes your chances of winning over a long period of time.
Football is obviously far more complex than blackjack. You’re not dealing with a handful of cards on a table with defined values, you’re dealing with the pure chaos of 22 of the world’s best athletes running around with an oddly shaped ball. However, statistics can still be instructive in certain situations and one of those situations occurred last night.
The Giants were down 20-6 in the 4th quarter when they scored their first touchdown of the night to make it 20-12 with 4:47 remaining in the game. Conventional wisdom would have the Giants kick the extra point and cut the lead to 7, hoping that they would be able to get the ball back and do it again to tie the game and force overtime. However, there is a very different way to look at this if you operate under the assumption that you are going to get that defensive stop and score a second touchdown (you have to assume this because any other scenario ends in a loss anyway). So let’s track the odds for the Giants to win the game working under that assumption.
Kick the extra point
Conventional wisdom says kick the extra point twice and try to get the game to OT. Since the extra point distance moved back in 2015, kickers have hit 94.0% of their extra point attempts overall. However, the Falcons play in a dome and kickers in domes have hit 95.9% of their extra points in domes since 2015 so let’s use that number to work with for this scenario.
If you miss the second extra point try (a 4.1% chance), you lose the game. However, if you miss the first extra point, you still get a chance to go for two and get overtime. Over the last 7 years, teams have converted two point conversions at about a 48.8% clip. Using that rate and the odds of winning an overtime game — 42.3% win, 15.4% tie, 42.3% loss based on current rate of ties with the 10 minute overtime period — you can calculate the chances of winning, tying, or losing if you miss the first extra point at 20.6% win, 7.5% tie, and 71.8% loss. Adding in the chance that you miss the second extra point (automatic loss) and applying those to your standard chances to win in overtime if you make them both, your win-tie-loss probabilities look like this:
Win: 0.041*(0.423*0.488)+0.959*0.959*0.423=0.397 (39.7%)
Tie: 0.041*(0.154*0.488)+0.959*0.959*0.154=0.145 (14.5%)
Loss: 0.041*(0.423*0.488+0.512)+0.041+0.959*0.959*0.423=0.459 (45.9%)
If you call a tie a half-win, you can boil that down to a win expectancy of 0.47.
You could always kick the extra point after the first touchdown and then try the two point conversion after the second, but going for it up front gives you the extra chance to make up for it if you don’t get the first one. If you’re going to go for two, after the first touchdown is the time to do it to maximize your odds.
Go for two
If you go for two after the first touchdown, here is how the odds play out. Again, we’re using a 48.8% league average two-point conversion rate and a 95.9% dome extra point rate.
You have a 48.8% chance of converting the first two-point try which leaves you with a 95.9% chance of winning the game on the second touchdown with an extra point. Even if you miss the extra point after the second TD, you get to overtime. So you have a nearly 50-50 shot of winning the game based on that scenario alone (which is better than your odds of winning in the scenario above), but you also have other roads to victory available even if you fail on the first two-point try.
If you don’t get the two-point conversion (which the Giants didn’t), you still get the chance to go for two a second time after the second touchdown to tie the game and force overtime. Here’s how the math tracks out with this route:
Win: 0.488*0.959+0.488*0.041*0.423+0.512*0.488*0.423=0.582 (58.2%)
Tie: 0.488*0.041*0.154+0.512*0.488*0.154=0.042 (4.2%)
Loss: 0.488*0.041*0.423+0.512*0.512+0.512*0.488*0.423=0.376 (37.6%)
Converting to a win expectancy, you get 0.60 which is quite a bit greater than 0.47.
Now, obviously there is some context to be considered here (as usual). Not all teams are created equal when it comes to two-point conversions. Some are better at it than others, but you would have to be converting at well less than a 40% clip to get to a break even point where kicking the extra point would be the smart play.
It’s also worth considering that teams that are big underdogs — which both the Titans and Giants were this weekend — typically don’t fare very well in overtime.
Was Vrabel right going for two?@JasonLisk makes the interesting point that LAC being the favored/better team is a factor that backs Tennessee going for it. My database says NFL teams favored between -4 and -9 win OT games 59.6% of the time (last 30 seasons; 7 ties in 190 games)— RJ Bell (@RJinVegas) October 22, 2018
There are plenty of factors that could skew the odds slightly in either direction, but the NFL averages point extremely heavily towards going for two in this situation.
The Giants ended up failing on the first two-point conversion and then allowing a long field goal by the Falcons that effectively put the game out of reach. They would come back and score late, go for two, and convert, but their onside kick attempt failed. Regardless of outcome, Pat Shurmur objectively made the right call on Monday Night and so did Mike Vrabel on Sunday morning. If the Titans come across a similar scenario later in the season I would hope — and expect — that they will go for two as well. Hopefully ESPN’s broadcasters will have caught on by then.