Vikings

Sam Bradford Dominates Invented "Sam Bradford Index," and That's OK

Photo Credit: Brian Curski

Sam Bradford set an NFL record for completion rate this last year, and it’s a credit to sports commentary that this wasn’t touted—by itself—as an elite accomplishment. That doesn’t mean Bradford played poorly, more that it’s become more widely recognized that completion rate by itself has become a misleading statistic.

As Chase Stuart at Football Perspective pointed out, Bradford accomplished this goal while placing dead last in yards per completion. Not only that, his record-setting accomplishment occurred in an era with higher completion rates overall, making that less impressive than when Ken Anderson accomplished the feat in 1982.

Inspired by this observation, Stuart wanted to look at which quarterbacks throughout history have been closest to the questionably noble deed of placing first in completion rate and last in yards per completion.

Using a common method of accounting for the different distributions of different statistics, he used the “z-score” (how many standard deviations a piece of data is from the average) of both completion rate and yards per completion to see who had the most dink-and-dunkiest quarterback seasons in history.

It’s not a bad thing—Sonny Jurgenson, Ken Anderson, Joe Montana, Fran Tarkenton, Steve Young and Drew Brees all place highly. It’s also not necessarily a good thing; luminaries like Chad Pennington, David Carr, Eric Hipple (who placed first in yards per completion in 1981 and last in 1986) and Kelly Holcomb also placed high on the single-season list.

Bradford’s 2016 ranked third in NFL history.

Christian Ponder’s 2012, surprisingly, only ranked 40th.

This doesn’t tell us much that we didn’t already know about Bradford’s season. We can add to that the context that the passing offense was meant to be a quicker-strike offense, somewhat reminiscent of the Chip Kelly offenses in Philadelphia (Bradford’s 2015 ranks 160th) and that the offensive line forced even more quick passes than usual.

But it does point us in the direction of what could be called his greatest area of improvement.

For a few years, I’ve been working on “implied yards per attempt,” and it generally works by multiplying accuracy rating (eliminating drops, throwaways and spikes) by average depth of target. The two measures have a fairly strong inverse relationship, so the quarterbacks who “over-complete” passes given how far they throw those passes grade well.

To me, it resolves the contemporary arguments that fans and analysts make that one should completely dismiss high completion rates because of checkdowns—if they work, why not?

Because this method strips away receiver drops, it puts the onus on the quarterback to make accurate passes given the difficulty of the attempt. It (perhaps unfairly) limits the impact of yards-after-catch, though because the final treatment ends up giving quarterbacks more credit for accuracy than deep passing, there’s some leeway.

With this approach, Bradford’s 2016 ranks 20th of 39 quarterbacks in the NFL.

Some quarterbacks with a high Sam Bradford Index have done really well in Implied YPA, while others have performed abysmally. The 2015 leader (Kirk Cousins) in the Sam Bradford Index (SBI?) ranked seventh in Implied YPA, and the 2014 SBI leader (Drew Brees) ranked sixth in Implied YPA. On the other hand, 2013 Matt Ryan ranked 25th in Implied YPA, and 2012 Ponder ranked dead last in Implied YPA.

Because we know Bradford to be very accurate, does this mean he has to take more deep shots? Probably—though not because he leads his eponymous index.

Football Outsiders have a number of statistics that contextualize appropriate depth of target. The most telling one might be ALEX, or Air Less Expected, which measures the average distance between how many yards an offense needs to gain for a new set of downs and how far the quarterback actually threw it.

Yes, it’s a backronym for Alex Smith.

Sam Bradford ranked second-to-last (33 of 34) in ALEX. That means he was the second-largest offender in throwing passes before the marker on third down, and it’s one reason the Vikings ranked third-to-last in third-and-long conversion rate.

ALEX measures magnitude as well as rate; if Quarterback A throws two passes on third down and one is five yards behind the line of scrimmage on third-and-15 while the other pass is five yards ahead of the marker in the same situation, their ALEX is -7.5. If Quarterback B throws two passes to the line of scrimmage on third-and-seven and third-and-eight, they have the same ALEX.

Clearly, Quarterback A did more for their team despite having the same ALEX. To account for that possible discrepancy, Football Outsiders has Failed Completions, which determines the rate at which a quarterback completes a pass that nevertheless keeps the offense off schedule.

Unfamiliar with failed completions? They are one of the quickest statistics we can measure from the season’s play-by-play data. A failed completion is defined as any completed pass that fails to gain 45 percent of needed yards on first down; 60 percent of needed yards on second down; or 100 percent of needed yards on third or fourth down.

Bradford ranked 32nd of 34 quarterbacks in failed completions per attempt and 28th in failed completions per completion. He had the third-most failed completions of any NFL quarterback since 1989.

This isn’t damning by any means; it’s more an opportunity for improvement. If one subtracts failed completions from overall completions, one effectively gets “successful completions per attempt” which is a better way to measure holistic success than only looking at failed completions. In that measure, Bradford finishes 10th.

These three approaches only identify where a player may improve, however, and don’t tell us if a player has the capability of improving in that area. We do have some clues as to what might inform that playing style for Bradford and whether or not he can still be successful outside of it.

And, of course, Football Outsiders has some of those tools. Passing Plus-Minus measures how many completions above expected (in this case, above average) given down, distance and pass location.

It’s a more granular approach than Implied YPA because it works off of each individual pass and compares that pass to a probability of completion for each throw for individual values by yardage, pass location (right, left or middle), down and distance.

A passing attempt thrown to the middle of the field 15 yards past the line of scrimmage on first-and-10 will be completed 60 percent of the time. A completed pass in that situation is worth 0.4 in passing plus-minus and an incomplete pass is worth -0.6.

Bradford ranked third in Passing Plus-Minus in 2016, with 28.4 more completed passes than expected. He also ranks third in Passing Plus Minus percentage (+5.5%), which takes into account total attempts.

That alone doesn’t tell us everything; if a player throws 300 passes exactly one yard downfield and completes all of them, they’d have a Passing Plus Minus of +66.0 and a Passing Plus-Minus percentage of +22.0%

But Football Outsiders very helpfully breaks down Sam Bradford specifically:

Then we get to Bradford at No. 3 with a season that ranks 23rd since 2006. I have to admit, his numbers came out much better than expected. This is also true when you break down Bradford’s plus-minus by the different ranges on the field.

Not surprisingly, Bradford did most of his damage on the shortest throws from 5 yards or less, and it was the medium range that gave him the most trouble with a ranking of 18th in the league. However, his deep passing was still adequate, and it’s not like he was afforded much help from his offensive line, running game, or receivers. We can view Bradford’s season in a better light than, say, David Carr in 2006, when he mostly dinked and dunked his way to a plus-27.3 season, but Bradford’s season still doesn’t hold a candle to Brees in 2016 (or 2011 for that matter).

Hey, there’s David Carr again.

Offensive coordinator Pat Shurmur might have designed shorter passing plays because Bradford was clearly the best in the league at such passes. The quarterback himself might have checked down more often because of how confident he was in that style of passing.

Bradford was a little below average with midrange passes and above average deep downfield. Football Outsiders wasn’t the only one who found talent in Bradford’s ability to push the ball. Pro Football Focus measured every quarterback’s deep ball throwing (measured as passes beyond 20 yards) by accuracy rate and found that Bradford led the league.

But Bradford was also the quarterback who threw the ball deep the least.

The offense’s unwillingness to move the ball downfield is one reason why Bradford could have the sixth-best passer rating and fourteenth-best adjusted net yards per attempt but the Vikings offense but ranked 19th in drive success rate (essentially a measure of first down production) and 23rd in points per drive.

Naturally, other big factors played a role in that. Below-average after-catch yards from the receiving corps and one of the worst running games in history plays a large (likely larger) role.

Imagining a similar Vikings offense but one that converts third-and-long (despite their abysmal running game, they converted third-and-short fourth-best in the league) can be salivating when paired with a top-five defense.

In theory, if he throws those passes more often, the Vikings offense will succeed more often.

Things don’t always work out like that—Bradford might only throw deep passes when he’s particularly confident in what he’s seeing. If he’s only throwing mid-range and deep passes only when it’s easiest, then a more aggressive playing style wouldn’t translate into more success.

If Bradford is playing at game-theory equilibrium—if he’s already maximizing his passing outcomes by passing exactly as often as he should have at every depth—that’s not terrible.

One can look at where he ranks in a number of passing metrics to get a sense of how effective that really is (plus, this year he’ll theoretically have the benefit of an improved offensive line and running game):

So somewhere between the 80th percentile (seventh or eighth of 34 quarterbacks) and the 45th percentile (19th or 20th of 34 quarterbacks). That’s not very clear, and Bradford is somewhat unique among quarterbacks in having this wide of a spread.

Honestly, if one takes the laziest approach and splits the difference, that puts him at about the 14th-best quarterback in the league. That’s a bit above average and fine for producing with a new running game at one’s back and an excellent defense.

But if Bradford can be more aggressive even if his efficiency downfield drops—that is if he’s average deep and a little below average in intermediate ranges—he could crack the top eight for quarterbacks.

It will also mean he won’t have to lead the league in the Sam Bradford Index, too.

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