Explaining the True Passer Rating: Addressing the Limitations of Legacy Metrics
- IamCogs
- Jun 18
- 8 min read
Nine months ago, Secret Base released a video titled "Correcting the NFL’s passer rating lie" which takes a wonderfully deep dive into how limiting the NFL Passer Rating truly is when it comes to accurately representing how well—or how poorly—a quarterback actually played. Its rigid constraints on maximum (158.3) and minimum (0.0) values make it a flawed metric.
I loved it.
But it got me thinking: in today’s modern NFL, there has to be a better way to quantify a quarterback’s performance. One of the most well-known issues with the NFL Passer Rating is how it measures efficiency using yards per attempt (YPA). This stat, of course, can be heavily influenced by a wide receiver’s ability to gain yards after the catch (YAC).
Here’s a simple thought experiment:
Quarterback A throws one pass—a 70-yard touchdown. However, 65 of those yards come after the catch, with the Wide Receiver turning a 5-yard slant into a long score.
Quarterback B also throws a 70-yard touchdown, but in this case, only 20 yards come after the catch. The QB hit his receiver perfectly in stride on a go route.
Are these two throws equal?
Both quarterbacks would end up with the exact same box score:
1/1, 70 yards, 1 TD, 158.3 Passer Rating.
On paper, they’re identical. In reality, one was a simple slant that turned into a highlight thanks to the receiver, while the other was a perfectly executed deep throw requiring timing, arm strength, and precision. Yet the NFL Passer Rating can’t tell the difference. So, let's fix that.
My True Passer Rating aims to do just that.
Using the True Passer Rating (TPR), those identical box scores tell a very different story:
5-yard slant turned 70-yard TD: 712.5
50-yard bomb in stride for a 70-yard TD: 1087.5
Same stats on paper. Vastly different performances.
Of course this is an extreme example of the system, but the point remains, not every throw is made equal.
TPR is a custom quarterback evaluation formula crafted to go beyond traditional metrics, specifically NFL Passer Rating. It’s designed to provide a more balanced and insightful view of a QB’s actual performance by factoring in:
Efficiency (YPA, Completion %)
Playmaking (TD rate, aDOT)
Mistake avoidance (INTs, Fumbles, Sacks)
Aggressiveness and sustainability (depth vs. accuracy)
Why (in my opinion) It’s Better Than Passer Rating:
Metric | NFL Passer Rating | True QB Rating |
Considers sacks | ❌ | ✅ |
Includes fumbles | ❌ | ✅ |
Evaluates aDOT | ❌ | ✅ |
Penalizes overreliance on short passes | ❌ | ✅ |
Caps bonus components | ❌ | ✅ |
Min/Max rating | 0.0/158.3 | Uncapped |
TPR is a more accurate and modern metric. It does this by accounting for the full context of a quarterback's performance—not just the outcome of a play. Unlike the NFL Passer Rating, which treats all yards and touchdowns the same regardless of difficulty or decision-making, the True Passer Rating differentiates between a routine screen pass and a perfectly placed deep ball. It incorporates factors like air yards, sack avoidance, and turnover impact to better reflect a quarterback's actual contribution to each play. Yes, sacks and fumbles that are the quarterback’s fault are part of the evaluation in TPR as well. Modern analytics have highlighted just how significantly sacks can impact EPA (Expected Points Added)—often as much as, or more than, turnovers. A great example of this comes from the 2024 Week 10 Sunday night matchup between the Detroit Lions and Houston Texans:
Jared Goff: 5 interceptions, 0 sacks, total EPA: -17.2
C.J. Stroud: 2 interceptions, 4 sacks, total EPA: -17.1
Despite committing three fewer turnovers, Stroud’s four sacks nearly erased that advantage, leaving him with virtually the same negative impact as Goff. This shows how costly sacks can be—and why any serious QB metric needs to account for them.
Downsides of the True Passer Rating:
No metric is perfect—and the True Passer Rating (TPR) is no exception. While it's a significant improvement over traditional Passer Rating, it does have a few limitations.
First, because TPR includes average depth of target (aDOT), it's far more effective as a game-by-game metric than a season-long one. Over the course of a season, the highs and lows of aDOT tend to normalize, and any bonuses or penalties applied by the formula are muted. Most quarterbacks cluster near the league average in aDOT, which can reduce the metric’s ability to differentiate performances over longer time spans.
Second, as shown earlier, TPR can produce extreme rating values for specific plays or short stretches. However, over the course of a full game, these usually balance out. I personally view these extremes as entertaining outliers rather than actual flaws. 😊
Lastly, "QB-fault" sacks are inherently subjective. Determining whether a sack is the result of a quarterback’s decision-making or external factors (like poor blocking) varies by the eye of the evaluator. That means there will naturally be some rating variance from game to game based on interpreter. I’ll be sharing more details soon about how I define a QB-fault sack in a future post.
Components and Calculations of the True Passer Rating:
TPR evaluates QB performance across 6 dimensions, then averages them and scales the result to a uncapped scale (with 100 as a general “solid performance” baseline.)
The formula components are:
Completion %
Yards per Attempt (YPA)
Touchdown Rate
Turnover Avoidance (with extra penalty for 2+ turnovers)
Sack Avoidance
aDOT Bonus (Directional)
So, let’s define those components into variables:
Variable | Definition |
CMP | Completions |
ATT | Attempts |
YDS | Passing Yards |
TD | Touchdowns |
INT | Interceptions |
FUM | Fumbles (lost) |
SACK | Sacks Taken |
aDOT | Average Depth of Target |
Some basic parts of the overall formula:
Completion Rate = CMP/ATT (unchanged from old NFL Passer Formula)
Yards Per Attempt = YDS/ATT (unchanged from old NFL Passer Formula)
Touchdown Rate = TD/ATT (unchanged from old NFL Passer Formula)
Turnover Rate = INT+FUM/ATT (Fumbles now counted in addition to Interceptions)
Sack Rate = SACK/ATT+SACK (NEW: QB at fault sacks are now counted against the QB)
Turnover Count = INT + FUM (This is used to add a bonus or penalty to the formula)
Now let's breakdown how this changes things with an example game:
21/30
180 Yards passing
2 Touchdowns
2 Interceptions
1 Fumble
1 Sack
9.0 aDOT
1. Completion % Bonus (C)
Rewards accuracy, Subtracts 30% (baseline for functionality)
Formula: (Comp% - 0.3) * 5
Bonus scales up to 3.5 (if 100% completion)
Example: 70% → (0.7 - 0.3) * 5 = 2.0
2. Yards per Attempt (Y)
Measures efficiency per throw
Bonus: (YPA - 3) * 0.25
If YPA < 5.5 → it's harshly penalized (multiplied by 0.1) (YPA - 3) * 0.1
Example: 4.0 YPA → (1.0) 0.25 0.1 = 0.025
3. Touchdown Rate (T)
Encourages scoring
Formula: (TDs / Attempts) * 20
Example: 2 TDs on 30 attempts → 2/30 × 20 = 1.33
4. Turnover Avoidance (TO)
Penalizes INTs + Fumbles
Formula: 2.375 - (TO rate * 25), scaled ×2
Capped at a +2 bonus (to avoid over-rewarding clean stat lines with bad production)
subtract 0.5 for each turnover beyond 2
Example: 3 turnovers → -0.75
5. Sack Avoidance (S)
Evaluates how well the QB avoids sacks relative to total drop backs
Formula: 2.375 - (sack rate * 30), scaled ×1.35
Capped at +1.5 max bonus
Bad sack rates can yield negative scores
Example: 1 sack → 1.50
6. aDOT Directional Bonus (A)
Encourages smart aggression
Penalizes short passing (aDOT < 7), rewards deeper throws (aDOT > 7)
Halved if completion % < 55%
Formula:
If aDOT > 7: aDOT - 7 / 2
If aDOT < 7: - (7 - aDOT / 2)
Rewards deep passes, penalizes excessively short ones
Example: aDOT = 9.0 → (9 - 7)/2 = +1.0
FINAL FORMULA:
True Passer Rating = ((C + Y + T + TO + S + A) / 6) × 100
Plugging in our examples ((2.0 + 0.025 + 1.33 - 0.75 + 1.50 + 1.00) / 6) × 100 = 85.1
This passing performance using the standard NFL Rating would be 79.9
A 79.9 NFL Passer Rating places this performance below the league average of 87.1, trailing by 7.2 points. Similarly, a True Passer Rating (TPR) of 85.1 also registers as below average compared to the TPR baseline of 100.0, falling short by 14.9 points. However, this outing could have rated significantly worse under TPR if not for the quarterback’s accurate aggression—completing 70% of his passes with a 9.0-yard aDOT—and his ability to limit sacks.
Using TPR (True Passer Rating), we can evaluate individual game performances against the following benchmarks:
~100: Solid start
150+: Elite performance
0–70: Rough outing
Below 0: Disastrous performance
These baselines provide clearer context for interpreting a quarterback’s impact on a game beyond traditional passer rating metrics.
True Passer Rating in Action
Now let’s take a look at how TPR reframes previous performances—starting with Caleb Williams’ Week 3 start against the Colts. Williams completed 33 of 51 passes for 363 yards, 2 touchdowns, and 3 total turnovers (2 interceptions and 1 lost fumble). He was sacked twice and posted an impressive 11.2 aDOT. His NFL Passer Rating for the game was a modest 80.8.
However, through the lens of TPR, the performance takes on more nuance. Despite the turnovers, Williams showed accurate aggression—completing 64.7% of his passes while pushing the ball downfield with an 11.2 aDOT. He also protected himself relatively well, taking just 2 sacks across 57 dropbacks. Plugging those numbers into the TPR formula, we arrive at:
The result? A 140.0 TPR, representing a net improvement of +59.2 points over his traditional NFL Passer Rating. Suddenly, Caleb’s ability to aggressively push the ball downfield while minimizing negative plays—particularly sacks—is properly recognized. This is a perfect example of how TPR captures value that the standard metric often overlooks.
Now let’s look at the inverse: Week 14 against the 49ers. On paper, this performance appears efficient—Williams completed 17 of 23 passes for 134 yards, 2 touchdowns, and lost 1 fumble. He posted a strong NFL Passer Rating of 116.9
But the surface stats don’t tell the whole story.
Williams took 5 quarterback-responsible sacks and averaged just a 6.8 aDOT, signaling a far more conservative approach. When these numbers are run through the TPR formula, we get a more complete picture of the performance’s true efficiency and impact.
The performance yields a TPR of just 41.9, a massive drop of 75.0 points from the traditional rating.
This stark contrast highlights one of TPR’s biggest strengths: it penalizes conservative play and negative impact plays (like sacks and fumbles) more appropriately than legacy passer metrics. While the NFL rating may paint this as a highly efficient outing, TPR reflects the underlying inefficiencies and missed opportunities that hurt overall offensive output. Let’s take a look at one more game.
Week 5: Panthers at Bears — a performance many consider one of Caleb Williams’ best of the season. He completed 20 of 29 passes for 304 yards, 2 touchdowns, no turnovers, took just 1 sack, and posted an 8.0 aDOT. That stat line earned him a 126.2 NFL Passer Rating—already an impressive mark by traditional standards.
But what happens when we run this performance through the TPR formula?
Williams checks every box here: accurate, aggressive, efficient, and clean. With strong downfield intent, no negative plays, and minimal pressure absorption, this game is a prime candidate for a high TPR score.
The result is even more impressive: a TPR of 153.3, marking a +27.1 point increase over the traditional metric.
This start checks every major TPR box: efficient downfield passing, no turnovers, and minimal sack impact. It’s the type of performance where both rating systems agree, but TPR further emphasizes just how dominant and clean the outing truly was—pushing it into elite territory by TPR standards.
What's Next?
Moving forward, all of my quarterback evaluations will include True Passer Rating alongside the traditional NFL Passer Rating to provide a more complete picture of performance.
While the NFL Passer Rating can offer a quick snapshot of efficiency, it often glosses over key contextual factors—such as sack avoidance, turnover impact, and depth of target—that significantly affect a quarterback’s actual value on the field. TPR corrects for these blind spots, rewarding aggressive but accurate play, penalizing avoidable negative outcomes, and capturing the true impact of a quarterback's decision-making and execution.
As we saw in the examples above, games that look solid—or even great—on paper can unravel under closer scrutiny (Week 14), while other performances (Week 3) reveal much more value than their surface-level stats suggest. And in elite outings like Week 5, TPR doesn’t just confirm greatness—it quantifies why it was great.
Including TPR in every game review will ensure a more nuanced, balanced, and analytically grounded evaluation going forward.