Column: Duke's offense struggles to convert third downs and run the ball. Does it matter?

Twenty-nine points is a decent mark for a college football team to end a game with. In fact, Duke football is 14-3 in the last three seasons when it scores at least 29 points, including a decisive win against Research Triangle rival N.C. State. Quarterback Maalik Murphy threw for three touchdowns in one of his best games of the year. 

But the final score doesn’t tell the whole story; the Blue Devils reached 29 points despite failing to convert a single third down on nine attempts. In fact, Duke has struggled immensely on third downs throughout the entire season. The program ranks sixth-to-last out of all FBS schools with a dreadful 28.9% conversion rate, with 3-6 FIU, 4-5 Houston, 1-9 Florida State, 1-8 Southern Mississippi and 0-10 Kent State the only teams below it.

Clearly, Duke struggles to move the ball on offense, especially on third downs. What causes those struggles, and more importantly, does it even matter for the Blue Devils’ success this season?

Success rate, explosiveness and expected points allowed

Before diving into Duke-specific metrics, it’s important to have a basic understanding of a few key statistics that measure offensive performance. Success rate is a statistic used to measure how successful an offensive play is relative to down and distance. In order for a play to be successful, it must gain at least 50% of the yards to go on first down, 70% of the yards to go on second down and 100% of the yards to go on third or fourth down, according to collegefootballdata.com (CFBD).

Explosiveness is a different statistic that measures the magnitude of successful plays. In turn, it uses yet another statistic called expected points added (EPA). This calculates the probability of a team scoring on any given play “based on down, distance and field position."

During the Blue Devils’ Sept. 28 victory against North Carolina, Murphy threw a touchdown to running back Star Thomas on second-and-17 from the Tar Heels’ 29-yard line. CFBD estimated a play run with that down, distance and field position produces 3.088 expected points, as opposed to the six that actually came from it.

While certainly not the end-all, be-all of measuring offensive efficiency, success rate and explosiveness can show how well football teams gain yardage — especially in crucial moments such as third downs. Indeed, these statistics together paint a picture of the Duke offense that struggles to move the chains, yet has earned seven wins through 10 games.

As shown here, the Blue Devils are one of the worst rushing teams in the FBS. Their run plays are successful at an alarming 34.7% rate, and their successful plays rarely yield strong returns. When considering that Duke averages 3.2 yards per rush attempt, one of the lowest figures in the FBS, this statistic is hardly a surprise. 

Why are Duke’s running plays so unsuccessful? CFBD includes a statistic called “stuff rate,” which measures the percentage of running plays where the runner was tackled at or before the line of scrimmage. Figure 2 compares FBS teams’ success rate on running plays to their stuff rate. The best running teams will have a high success and low stuff rate, indicated in the bottom-right quadrant.

Figure 2

As shown in this graph, there is a negative correlation between a high number of running plays that are stopped at or before the line of scrimmage and the overall success rate of these plays. For example, Army, one of the most aggressive running teams in all of college football, have the lowest stuff rate and highest success rate on run plays. Meanwhile, the Blue Devils are stuffed on nearly a quarter of their running plays, limiting their success in running the football.

It is clear that Duke faces extreme difficulty in moving the ball on the ground — but what about through the air?

Passing promise?

Figure 3 displays FBS teams’ success rate versus explosiveness on passing plays, where teams closer to the top-right quadrant will have more success and generally larger gains on these plays. Duke’s location on this graph is indicated by the orange arrow.

Figure 3

Compared to its subpar rushing attack, Duke’s passing offense is roughly average in success rate and explosiveness. For the season, the Blue Devils have a success rate of 41.5% on passing plays and gain 1.587 expected points per successful play.

However, Duke’s passing game has had its ups and downs. Figure 4 shows FBS teams’ passing success rate and explosiveness from Weeks 5 through 8, which encompass the North Carolina, Georgia Tech and Florida State games for the Blue Devils.

Figure 4

Through these three contests, Murphy struggled immensely, completing just 50.6% of his passes and throwing for three touchdowns. As such, the Blue Devils were successful on just 30.4% of their passing plays, one of the lowest marks in the FBS over this time period.

However, the redshirt sophomore quarterback has had a nice run of form, averaging 288.3 passing yards per game over his last three contests while throwing for eight touchdowns. Figure 5 displays the same metrics as Figure 4 but for Weeks 9 through 11, which include Duke’s contests against SMU, Miami and N.C. State.

Figure 5

As shown in the graphic, Murphy’s statline has improved during Duke’s past three games. It remains to be seen whether he will keep up this proficiency; Virginia Tech has a strong passing defense, while Wake Forest has arguably the worst such unit in the ACC.

Ultimately, the 2024 Blue Devils’ biggest strength is neither their passing nor rushing offense. It is their defense, which has allowed just 22.1 points per game, one of the lower marks in the country. For the remainder of the season, Duke should continue to lean into its defensive tenacity as Murphy and his receivers move the ball on offense. If all goes according to plan, the Blue Devils could achieve a strong bowl game in the short run — and a blueprint for future Diaz-Brewer coached teams in the long run.