In the aftermath of Monday night’s contest between the Houston Texans and Tennessee Titans, several people have pointed out the outstanding numbers Titans quarterback Marcus Mariota compiled in a losing effort:
Marcus Mariota stats:
22-23 passing, 303 yards, 2 TDs, 0 INTs, 147.7 passer rating
His team lost by 17 points.
— Kevin Patra (@kpatra) November 27, 2018
Anyway you slice it, those numbers are crazy. While sports-analytics nerd (his words, not mine) Adam Steele pointed out that Adjusted Net Yards / Attempt, which includes Mariota’s six sacks taken, does a better job capturing his overall value, Mariota’s ANY/A comes out to 10.3, still an excellent total. For reference, New Orleans Saints QB and MVP frontrunner Drew Brees leads the NFL with a 9.7 ANY/A.
So if Mariota performed so well, why didn’t the Titans score more than 17 points?
Empty Yards and Completions
First, it’s important to note what Mariota’s 22 of 23 for 303 yards statline includes—and what it doesn’t. It includes Mariota going five of six for 64 yards in what amounts to garbage time—a drive that started with less than two minutes left, at his own nine yard line, with a 17-point deficit. It does not include the six sacks for 43 yards Mariota took. And these sacks were killer:
That’s right—all six sacks led immediately to punts or led to long-yardage situations that resulted in punts. Six sacks, five drives killed. While the negative yardage factors into ANY/A, and the extra plays into the denominator, it sells short the effect negative plays have on drives. An eight-yard loss and an eight-yard gain are not equal. The gain might convert a first down or set up a 2nd-and-2, but once the offense gets the first down, the O and D start back at square one: first and 10. An eight-yard loss is practically a drive killer, dramatically reducing the chance of converting a first down and virtually handling the ball to the other team. Rarely is this effect as dramatically shown as it was Monday night.
Mariota’s completion percentage was also raised by what Football Outsiders’ Scott Kacsmar calls “failed completions,” that is, completions that don’t help the team. For instance, Mariota was seven of seven passing on third down, but four of those completions didn’t net a first down. Chase Stuart identifies seven completions that produced a negative Expected Points Added. Add that to the six sacks and six passes in garbage time, and you only have 10 relevant pass plays that helped the Titans.
Also worth noting: Mariota added 28 yards on six carries, but these were also pretty hollow. He had a 14-yard scamper to convert a 2nd-and-13, but that was his only run that converted a first down.
Big Play Distortions
And there’s an issue with those 10, too—specifically, two of the plays were too good. Obviously the being good isn’t a problem, and the two big play touchdown passes, a 61-yarder to tight end Jonnu Smith and a 48-yarder to wideout Corey Davis, put Tennesee’s only two touchdowns on the board. The problem is the distorting effect these plays have on Mariota’s per play statistics. Two plays were responsible for more than a third of his yardage total, bumping up his yards per attempt from 9.2 to 13.1—an increase of almost four yards!
Statisticians have long known of the distorting effect outliers such as these have on averages, but they’re especially misleading when it comes to measuring football efficiency. That’s because plays are not a finite resource. Get a first down, and you can earn more plays. Many statistics will show one 40-yard completion as more efficient than eight five-yard gains, but the two teams are in the same state at the end: 40 yards downfield, facing a first-and-10. (Clock considerations make the two situations not exactly identical, but in many situations eating more time of possession in the second scenario is preferable). Had Mariota thrown five shorter passes instead of the one 61-yarder, still getting a touchdown, it’s worth the same on the scoreboard but would not have distorted his stat line so dramatically.
Mariota’s ANY/A was 74.5 on the two touchdown drives and 10.7 in garbage time, but a paltry 4.1 on the other seven drives despite a gaudy 15-for-15 completion mark:
Add it all up and Mariota’s outing is practically a perfect storm of the ways conventional statistics can be distorted—outlier big gains, failed completions, costly sacks, and garbage time production. The Titans passing game wasn’t completely toothless, but it struggled much of the night, a reality you’d never know from Mariota’s stat line.
What Wasn’t His Fault
The passing game was hardly the only problem for Tennesee Monday night. The defense gave up 34 points, and it also did the offense no favors, generating zero turnovers. That left the offense with an average starting field position of their own 25—a figure that would rank 31st over a full season.
The running game was superficially successful—23 carries for 105 yards—but it falls prey to the same big play distortions that the passing game does. Davis took an end around for 39 yards, and there were also Mariota’s contributions on the ground, discussed above. Running backs Derrick Henry and Dion Lewis combined for 15 carries for only 38 yards, so the down-to-down running game wasn’t helping any. Backup tight end Luke Stocker was also stuffed on a 4th-and-1 rush attempt near the goal line, a key play in a game that was 14-10 at the time.
Where We Go
Mariota’s stats are misleading, but that hardly means we should throw out all statistics. Savvy analysts need to understand what statistics tell us, and what they don’t. Superior metrics will punish quarterbacks for sacks and avoid excessively rewarding them for completions that don’t work towards moving the chains or garbage time yardage. It’s worth noting that in ESPN’s proprietary QBR, Mariota ranked only 24th among Week 11 QBs at 50.3. Perhaps other statistical innovations, such as moving from a per-play to a per-drive basis, have not been invented yet. There are two kinds of mistakes with statistics: ignoring them entirely, and using them without understanding limitations and context. Marcus Mariota’s line Monday is a perfect illustration of the latter.