.png)
Football's never really been a statistics-driven game. For the longest time, NFL offenses were predicated on run plays, slowly wearing out the opposing team in an effort to grind out the win. Flash forward to the present day where the infusion of analytics into professional sports has led to the modern pass-first offense. With this new ariel play style has come higher expectations on Quarterbacks, who are now expected to lead offenses with their arm on a nightly basis.
The biggest question that comes from this is the issue of assigning value to a QB. In such a team-driven sport like football, each player's individual contribution to winning becomes nearly impossible to approximate. This is especially true for the QBs who function as the leader of the team. Win or lose, the credit or blame is headed in their direction. It's certainly feasible to use win rates, but nobody would argue that Jimmy G is one of the most valuable passers in the league right now. Passing Yards provides some indication as well. However, even at 44, Tom Brady's league-leading 5,316 yards don't account for his personnel, schedule, or number of attempts.
Enter QBR, the proprietary ESPN metric for ranking Quarterbacks. QBR assigns a value between 0-100 for every QB based on their performance in certain areas. In contrast to a stat like PER from the NBA, QBR does not solely measure production. It accounts for a variety of factors that analysts tend to criticize about commonly used counting metrics.
The QBR metric is intended to factor in context by analyzing performance at the play-by-play level. As fans viewing the game, we are able to interpret the difference between a 7-yard pass on 2 and 7 vs a 7 yd pass on 3 and 15. While both are 7 yards, something that most people wouldn't look past, one player better contributes to the team winning percentage because it gives them more opportunities to score the ball. By accounting for factors such as yards for a first down, yards to the endzone, and time left in the game, a formula is used to create an "expected points" or EPA metric. After each play, the EPA changes, and this positive or negative change indicates whether a play is successful or not. For this reason, turnovers change in terms of their overall negative value depending on when they occur as well. A game-winning attempt that leads to an interception is weighted differently than a fumble on the opening drive. QBR even factors in penalties.
The most valuable aspect of QBR is how it allocates credit for each player on the field. Depending on the number of yards traveled in the air, time under pressure, and the percentage of the yards that were gained after the catch, the change in EPA will be distributed amongst the QBs Offensive Line and WRs differently.
Out of the top 10 QBs in QBR for the 2021 NFL regular season, 7 made the playoffs, 2 were eliminated in week 17, and 1 was injured for most of the season. With just 1 number, we can come up with a list that includes all of the widely regarded best QBs in the league based on the "eye-test."
A study by the Michigan Football Society further analyzed the effectiveness of the QBR metric as it relates to wins.
As seen in the bar chart above, EPA based metrics and QBR tend to be the strongest indicators of team succeses.
Despite this, their study also found these statistics to be highly variable from year to year and classified EPA and QBR as bordering on"slightly unstable" metrics when viewed exclusively by themselves.
It is important to note that QBR is an efficiency stat, not a production stat. It measures how well players produced per play, but does not indicate their total level of contribution in a game. QBR does contain certain flaws. In particular, it fails to account for both scalability of player's performance and the benefit of incomplete passes over taking sacks. Overall, QBR is a quite nuanced indicator of Quarterback skill, and I have yet to see a widely used 1-number metric in any other sport that accounts for this much variability in a game.
Comments