Injuries matter less in the NFL than you think

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Injuries matter less in the NFL than you think

Losing expensive players to injury - quarterback excluded - is not as fatal to a teams' success as is often suggested, study finds

EVANSTON, Ill. - New research from Northwestern's Kellogg School of Management finds that injury matters less in the NFL than is often assumed. With the exception of highly paid quarterbacks, losing players - even the high-dollar ones - to injury is not as fatal to a team's success as one might think.

"Ultimately, the NFL is a 'next man up' league, where non-stars fill the role of stars reasonably well. My research shows that the team of the injured player would not see a substantial change in their on-field success, the only exception being the highly paid quarterback," said Joel Shapiro, clinical associate professor of managerial economics and decisions sciences and lead author of the study.

The study, which was published in Sports Economics Review earlier this month, suggests that passing on a talented player because he's injury-prone, or paying heavily to replace an injured starter midseason, may cost more than the injury and recovery itself. The findings indicate spending money on depth may go further than spending money on durability.

"Executives who want to build a winning team need to ask hard questions about their star players," Shapiro said. "If a backup can fill in for a few games without a lot of negative impact on winning, how much does the star really add? Our research suggests the answer is 'less than their pay suggests.'"

Method

NFL teams spend exorbitant amounts of money on players when building out rosters. The injury risk of the potential players often factors into the contract decisions in the front office. Shapiro measured how much success a team gives up when a percentage of payroll is unavailable due to injury.

The study analyzed two primary data sources covering NFL regular seasons spanning from 2012 through 2022. The player-level dataset contained 22,584 player-season observations across 6,235 unique players - linked to a specific team and season. The team-level dataset contained seasonal win totals, games played, win percentage and playoff qualifications for all 32 franchises across the study period.

Shapiro introduced a new measuring tool to weigh the impact of injury on a team: Percent Cash Wasted (PCW), which is the share of payroll paid to players while they're injured.

Using the data, Shapiro examined the relationship between PCW, team winning percentage and playoff qualification. He matched the players to their teams in each year to create a measure of PCW for each team for each year and then assessed how its PCW affected team success.

Shapiro explained the difference between his study and others in the field is quantifying the relationship between winning and the economic cost of injury. Measuring it for the first time is an important step for this domain, he said.

Findings

Researchers found that NFL teams are more resilient to injury than is commonly assumed: After controlling for expected team quality, a seven-percentage-point reduction in PCW created only one additional win over a 17-game season.

"Teams lose less payroll to injury than I assumed, about 10% in an average season," Shapiro said. "And that lost payroll costs fewer wins than I expected. Most assume a team could win noticeably more just by staying healthier. Our research shows it can't."

The study found that with most roster positions, the cost of injury is modest enough that teams may be overweighting it in personnel decisions.

"The exception is franchise quarterbacks, where evidence suggests there are far more apparent performance consequences for a team when the QB is taken out," Shapiro said.

He continued: "The difference in winning between a $10 million player and his backup is smaller than most people would think," Shapiro said. "An injury of the $10 million player puts far more payroll on the sidelines. At most positions, backups fill in reasonably well, so teams may be paying too much for durability."

A team needs to keep about 7% more of its payroll on the field instead of sidelined due to injury. On average, that means about $11 million in salary needs to be kept on the field to win one more game across the entire season.

"A healthy star still contributes, and at most positions his injury costs relatively little in wins," Shapiro said. "Quarterback is where the concentrated risk is real and where protecting the investment matters the most."

The data doesn't give explanation on why quarterbacks are the exception, but Shapiro theorizes it's simply because the quarterback is the most important position on the field. "He touches the ball on every offensive play, and most of the offense's decisions run through him," Shapiro said. "That makes the starter's health investment worthy."

Shapiro hopes his research helps executives make better decisions on how to allocate their payroll. "The next step is to assess what each dollar buys when the player is not injured," he said. "Measuring the contribution of stars relative to their replacements, position by position, would show where premium contracts earn their cost and where the money would win more games elsewhere on the roster."