FanPost

McCarthy's 4th Down Decision vs. the 49ers


Just when the Packers were starting to build a little momentum early in the 4th quarter while trying to get themselves back into the game against the 49ers, they suddenly found themselves facing a 4th and 5 at their own 49-yard line with 11:38 left to play in the game, down by 14 points. Rather than try to keep this momentum going and get the team into the end zone to make it a one-possession game, McCarthy decided to punt and try to pin the 49ers deep, with hopes of getting the ball back with little time lost, ideally in about the same position the Packers had just punted from. However, the 49ers never did give the Packers the ball back, at least not until they kicked off after scoring yet another touchdown to put the game out of reach.

Brian Burke at advancednflstats.com has done a very comprehensive study of 4th down situations in NFL games, which I highly recommend reading. You can find part one of his study here. The conclusion is that NFL coaches should be going for it on 4th down far more often than they currently do. You might say that coaches collectively are far too "risk-adverse," but in fact the strategies that coaches feel are safer are often the ones that are in reality much riskier. Field position is the most tangible component of a coach's decision, so they will often put too much emphasis on just that, but the correct decision is usually much more dependent on game score, time remaining, and retaining possession. I believe that coaches often play towards common misconceptions to avoid backlash from the media, the public, and the owners and general managers that do the hiring and firing.

Just how bad was McCarthy's decision in this particular instance? Brian Burke has created a 4th down calculator, which can be found here, to evaluate any 4th down decision coaches need to make. Here are the results from the calculator when we plug in the specifics from our game:

Packers49ers4thdown_medium

What do the statistics on the right mean? Let's begin with the first five lines of numbers. The first line talks about success rate, which is the historical probability of getting a first down for all teams on 4th and 5 in similar field position throughout recent NFL seasons. Given that the Packers have an above-average NFL offense, we can assume that their success rate would be at least 49%. The next three lines all reference EP, which stands for expected points. Expected points are the average points an NFL team in that down, distance, and field position can expect to score on the current drive. Included in this expectation are things like turnovers and even the kickoff after a touchdown or field goal. Note that from the compiled historical data, NFL teams can expect to score a net average 2.29 points if successful in this 4th down situation, while failing to convert the 4th down puts the opponent in a position to expect 2.11 points on average. A punt will put the opponent in a position where they can expect to score .26 points on average. Given these averages and the 49% conversion rate, the decision to go for it results in a net .05 expected points gained, while the decision to punt results in a net .26 expected points for the opponent. Just in case you think 49% is a little high, the break-even point where going for it would be equivalent to punting would only be where there was a 42% conversion rate.

All of the numbers above ignore the score and the time remaining in the game, and that's where the final five rows of numbers come into play. WP stands for win probability, which is the probability that the team with the ball will end up winning the game given the current score, down, distance, field position, and time remaining. Again, these figures are based on actual game situations throughout recent NFL history. Note that the Packers would've had a 6% chance to win the game if they had successfully converted the 4th down, and they would've had a 3% chance to win if they turned the ball over on downs. Also note that, probably due to some rounding, punting gives the Packers the same 3% chance to win. Again considering the 49% historical success rate of converting the 4th down, just the decision to go for it would've given the Packers a 4% chance to win, and the decision to punt gave them a 3% chance to win, meaning the decision to punt decreased our chance of winning by about 25%. Because the WP after failing to convert and after punting are basically identical, there isn't even a break-even point for going for it given the game situation. If the Packers had even a 10% chance of converting that first down, which they surely did, they should have gone for it.

Obviously there are many reasons the Packers lost this game, among those being the complete inability to stop Kaepernick's running, a stagnant 2nd-half offense, and some ill-timed turnovers. However, the Packers still had a chance to pull out the comeback in the fourth quarter, but McCarthy kicked that chance away. The Packers can contend for a Super Bowl again next year by making some personnel, scheme, and strategy changes, but it will also help to make the right choice in game management decisions, especially those as cut and dried as this one.

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