How Coaches and the NYT 4th Down Bot Compare

Even the boldest N.F.L. coaches can turn timid on fourth down. When a team fails to pick up enough yards on third down, coaches are faced with a few options. They can decide to kick the ball (by either punting or attempting a field goal) or they can decide to go for it. Going for it is risky – if they fail, they risk ridicule by every TV analyst, armchair quarterback and cabdriver in the country. Kicking is the safe, more conventional choice. But is it the right one? That’s where NYT 4th Down Bot comes in. It evaluates whether an N.F.L. team should punt, attempt a field goal or go for it on fourth down, in any situation. To make its decision, NYT 4th Down Bot uses a model developed by Brian Burke, founder of AdvancedNFLStats.com. According to the model (and thus, according to NYT 4th Down Bot), coaches are much more conservative than they should be. NYT 4th Down Bot works on the premise that for most of the game, a coach should be trying to maximize the point spread between his team and his opponent – that is, scoring as many points as possible while suppressing his opponent’s opportunities for points. Later in the game, other factors come into play (more details on that below), but when the score is reasonably close in the first three quarters and early in the fourth, point maximization is the name of the game. Here is a comparison of how a coach who truly maximizes points would behave on any fourth down anywhere on the field. On the right, the same chart showing how coaches have actually behaved since 2002.

What NYT 4th Down Bot Recommends on 4th Down What N.F.L. Coaches Do Most Often

The bot’s recommendations may seem aggressive, but they are the results of an analysis of N.F.L. games since 2000, including the success rate of fourth-down attempts and the value of having the ball at different places on the field. The difference is stark: coaches are much more conservative than they should be if they are truly trying to score as many points as possible. Too often, coaches forfeit the ball through a punt, for instance, when they have a solid chance to make a first down. The field position they gain from the punt is often not worth the missed opportunity to keep a drive going. Perhaps the most common mistake coaches make is punting or kicking a field goal on fourth and only a few yards. Recent football history suggests teams should often go for it on fourth and short even deep inside their own half of the field. By punting, they guarantee the other team will have the ball with good field position. By going for it, they are risking giving their opponents fabulous field position – but with the potential reward of keeping the ball. Obviously, the best strategy varies, depending on a team's strengths and weaknesses. But the overall pattern seems clear: coaches are far too conservative. How does NYT 4th Down Bot decide? NYT 4th Down Bot uses thousands of N.F.L. plays since 2000 to calculate the average number of points each situation is worth, a measure called expected points. (Expected points and its application to fourth downs is not new. It was created in 1971 by former N.F.L. quarterback Virgil Carter and Robert E. Machol and has been improved and refined in various ways since, notably with the book “The Hidden Game of Football” and David H. Romer's signature 2002 paper. NYT 4th Down Bot's model is similar to Mr. Romer’s, but has more seasons of data behind it.) With about 10 minutes left in the fourth quarter, NYT 4th Down Bot switches from maximizing points to maximizing win percentage. Win percentage measures how often teams who punted, attempted a field goal or went for a first down won the game. (This measure is more useful later in the game because it is easier to measure the impact of a single play on a game’s outcome.) Um, expected points? The measure assigns a single point value to any game situation, based on how likely a team is to score from that field position. Below is a chart of expected points on an average first down, depending on where on the field the first down is.