Advanced stats indicate huge potential for Zac Stacy


Alright guys, wake up Grandma and tell the six-year-old to turn off his DS because this column is about to pull into Extrapolation Station.

Before I jump into some serious numbers, however, I feel like it’s important to preface what I’m about to share with you by reminding everyone that, while impressing in both games, Rams rookie RB Zac Stacy has started only two NFL games in his young career. After earning his first start two weeks ago against the Jacksonville Jaguars, Stacy inspired enough confidence to earn another shot as the team’s premiere back last week against Houston.

A small sample size, obviously, but the impact that Stacy has had on the St. Louis offense during his brief time as a starter cannot be ignored. Both games, Rams victories by a combined margin of 72-33, provided viewers with a glimpse at how potentially lethal and efficient this offense can be. The Rams scored more than 30 in both games – something they hadn’t done all season – and after last week’s head-turning 38-13 victory over the Texans, fans were unmistakably left with visions of a righted ship.

When glancing simply at the box score, however, Stacy’s numbers over the past two weeks as starter certainly don’t blow wind up any skirts. Stacy’s 14 carries for 78 yards against Jacksonville and 18 carries for 79 yards against the Texans are decent numbers, but they aren’t necessarily reflective of the team’s (relatively) huge offensive outburst over the last two weeks. Stacy still hasn’t scored that elusive first career touchdown, and the Rams as a team are still without a rushing touchdown for the entirety of 2013.

Still, both of Stacy’s performances have felt much bigger than the box score suggests. Based solely on watching each game, it seemed like the rookie was consistently picking up the right yards at the right time. As it turns out, an advanced assessment of Stacy’s performances sheds an entirely different light on his contribution to the offense and puts him in some rather elite company.

Now, I’m not a huge metrics guy, but I absolutely recognize their added value in performance assessment. With that said, the stats professionals over at Pro Football Focus have developed a formula for determining a running back’s “Elusive Rating.” The resulting number is an attempt at measuring how a running back performs when he is “beyond the point of being helped by his blockers.” Essentially, it’s a look at how the back has performed when he’s all on his own. So, bear with me, because it’s about to get mathematical up in here. The rating is determined by taking the player’s missed tackles forced and dividing that number by the sum of the player’s carries and receptions. That number is then multiplied by the player’s yards after contact per attempt times 100. The resulting number is that player’s “Elusive Rating.” It can all be found here, but essentially it looks like this:

(Missed tackles forced)/(Carries + Receptions) x (Yards after contact per attempt x 100)

Maybe you all are stats wizards, but I only took one math class in college, so I certainly won’t blame you for rereading that once or 35 times like I did. Anyway, on the season, Stacy’s elusiveness measurements are remarkable. His seven missed tackles forced, 33 carries, two receptions, and 3.0 yards after contact per attempt average translate to a 60.0 “Elusive Rating,” which is good for sixth-best league-wide among backs with 30 or more carries. Indianapolis’ Trent Richardson and Minnesota’s Adrian Peterson top the list, and Stacy is rated as vastly more elusive than some of the NFL’s traditionally elite speed runners like Philadelphia’s LeSean McCoy, Kansas City’s Jamaal Charles, and Tennessee’s Chris Johnson.

Furthermore, his 3.0 yards after contact per attempt average is good for third-best league wide among backs with 30+ carries behind only AP and Houston’s Ben Tate. Again, take these numbers as you will, but they add some concrete definition to that basic eye test that Stacy certainly passed against Houston. The numbers suggest that if Stacy isn’t blowing up would-be tacklers, he’s most likely dragging them along with him.

Additionally, PFF uses a grading system for each player’s weekly performance that is as thorough as it is complicated. (A primer can be found here). Yet again, Stacy graded out near the top of the league in each of his first two starts. The Vanderbilt product earned the fourth-highest rating among all backs for his most recent performance, with his tally of +2.3 trailing only Houston’s Arian Foster (+3.3), Cincinnati’s Giovani Bernard (+2.8), and Arizona’s Andre Ellington (+2.6). While that rating includes contributions in the receiving game as well as pass blocking, if concentrated only on rushing plays, Stacy’s +2.1 grade was the NFL’s second-best on the week behind only Foster’s +2.2. It wasn’t just a one-week peak either. Against Jacksonville in his first start, Stacy came in sixth-best league-wide with a +1.4 overall grade and third-best on rushing plays at +1.3.

OK, still with me? What it all boils down to is that Stacy’s first two starting performances, while maybe not jaw-dropping upon first glance, are certainly cause for excitement going forward when further analyzed.

But again, because it’s worth repeating, it has only been two games. Looking ahead, the Rams visit Carolina this weekend where the stingy Panthers (stingy as in unwilling to budge, not like what a bee is) and their number one overall defense are giving up only 88.8 rush yards per game to opposing offenses. Also, their 13.6 points per game allowed on the season is good for second-best league-wide behind the Chiefs (still can’t believe I just wrote that).

Barring any unforeseen circumstances, Stacy will earn his third consecutive start on Sunday. If the Rams hope to continue their recent upward trend, it will absolutely hinge on the rookie’s ability to continue to assert himself in between the tackles against that stout Carolina defense.

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