Converting Between the College, NFL Passer Ratings

January 21, 2009

As long as quarterbacks have played the central role of offensive football, people have tried to quantify who is the best. Various methods have been concocted to do just that, and many more are being devised even today.

The two most widely-cited measures are passer rating and passing efficiency. The former is used by the NFL, while the latter is used by the NCAA.

They both are complex formulas, and if you want the details, hit up the passer rating Wikipedia page. Despite their differences, they use the same four components: completion percentage, yards per attempt, touchdowns per attempt, and interceptions per attempt. What differs is how the parts are weighted.

The NFL’s passer rating imposes a ceiling and floor on the four parts, so it has a lower boundary at zero and an upper boundary of 158.3. The idea is not to let outliers, good or bad, have undue influence on the rating. If you’re curious, the answer is yes, the pro game has seen its share of both perfect games and zero games.

The NCAA’s passing efficiency has no such boundaries against outliers. The maximum score occurs when someone completes every pass for a 99-yard touchdown and the minimum score occurs when someone completes every pass for a 99-yard loss. You are correct in assuming we’ve never seen anyone log a maximum or minimum score.

Despite there being pros and cons to each system, they are generally kept apart. The passer ratings of college quarterbacks and the passing efficiency of NFL quarterbacks are not widely reported.

Here are some tables that show some insight into how the systems differ and how we might compare the relative performances of collegiate and professional quarterbacks.

For the sake of brevity, I have included only the top ten of each category in the tables.

I Said Relative Performance

Before we get into numbers, I want to stress that any comparisons done between college and pro quarterbacks are meant to viewed in relative terms.

The NFL obviously has tougher defenses than college does, but the NFL also has better offensive lines and, well, quarterbacks too. I don’t think anyone would argue that the Peyton Manning of today is not better than the version of himself that lost to Florida four times at Tennessee.

Take the inter-division comparisons with a grain of salt, and know that this (like football) is in the end just for fun.

NFL Passing Efficiencies

I will start with passing efficiency of the primary NFL starting quarterbacks. I got my stats on them from ESPN’s stats page for the regular season, so if you’re looking for the passer rating standings, there you go.

2008 NFL Passing Efficiency
Rank Player Team Passing Efficiency Pass. Rat. Rank
1 P. Rivers SD 154.6 1
2 D. Brees NO 144.4 4
3 K. Warner ARI 143.3 3
4 C. Pennington MIA 142.1 2
5 M. Schaub HOU 141.1 7
6 A. Rodgers GB 139.3 6
7 P. Manning IND 139.1 5
8 T. Romo DAL 138.5 8
9 M. Ryan ATL 134.7 11
10 J. Garcia TB 132.8 9

Here, Philip Rivers still rules the roost. There’s a little movement in the rankings, but no one slides more than two spots one way or the other.

None of these numbers really pop out though, even Rivers’ mark. That is because college quarterbacks routinely achieve loftier numbers, such as Sam Bradford’s 180.3 mark that led the college game in 2008.

For comparison, Rivers’ efficiency score would land him at 14th-best in the country between Ball State’s Nate Davis and Nebraska’s Joe Ganz. There is a good reason why college quarterbacks can go higher than the pro guys, and while I think you know what it is, I’ll take a look at it later.

The lowest passer efficiency score was by Cleveland’s Derek Anderson. He managed a 103.0 passing efficiency. By comparison, the 100th-ranked college passer was Kentucky’s Mike Hartline with a 104.7 score.

College Passer Ratings

Now it’s time to see how the big men on campus fared using the NFL’s report card. Their stats came from the NCAA stats site.

2008 NCAA I-A Passer Ratings
Rank Player Team Passer Rating Pass. Eff. Rank
1 S. Bradford OU 127.0 1
2 T. Tebow UF 122.1 4
3 C. McCoy TEXAS 121.6 3
4 D. Johnson TULSA 117.7 2
5 C. Clement RICE 116.5 7
6 M. Sanchez USC 113.0 6
7 G. Harrell TTU 112.9 8
8 C. Keenum HOU 110.9 9
9 Z. Robinson OKST 110.2 5
10 C. Daniel MIZZ 107.5 10

As you can see, the college guys do better overall on the NFL’s scale too. In fact, Bradford’s season would shatter Peyton Manning’s all-time record of 121.1 for a single season. The other two Heisman finalists would edge him out too, for that matter.

There was a bit more movement in these standings after conversion than in the NFL standings, with Oklahoma State’s Zac Robinson taking the biggest fall at four spots. I don’t know if that has more to do with formulaic differences, but I have a feeling it has more to do with the fact that there are a lot of quarterbacks in I-A college football. The bunching that ensues means small real drops could get magnified as relative drops.

The lowest passer rating in the pros was by the Browns’ Anderson again with a score of 66.5. Kentucky’s Hartline, Mr. 100th Place in college, had a rating of 69.4.

You know there has to be something inflating the college stats. I mean the No. 32 college quarterback in passer rating was Illinois’ Juice Williams, and he managed to post an 86.4 rating. That would tie him for 14th place in the NFL with Eli Manning and Donovan McNabb.

Adjusted College Passer Ratings

The inflation factor was something we all know. They’re sweet, they’re fluffy, they’re cupcakes.

As I said above, I’m looking to judge relative value. NFL teams don’t get to stock up to a third of their schedule with arena league teams, but the top college teams can schedule anywhere from three to five teams (depending on the conference) that cannot compete on the top team’s level.

In 2008, the power conferences were the six BCS leagues plus the Mountain West Conference. Because I’m feeling charitable, and because their name is in the BCS contracts too, I counted the Fighting Irish of Notre Dame as a power team for this part too.

So, I took the top ten quarterbacks from these conferences and took out all stats against teams that are not power teams. You can argue that in 2008 Central Michigan and Troy were much better foes than, say, Washington or Washington State, and you’d probably be right. Even so, I had to draw the line somewhere.

Here is what the passing efficiency stats look like for the top college quarterbacks from power teams against power teams:

Top QBs from Power Teams Against Power Teams
Rank Player Team Pass. Eff. Adj. Pass. Eff. Diff.
1 S. Bradford OU 181.0 180.8 +0.2
2 T. Tebow UF 166.3 172.4 -6.0
3 M. Sanchez USC 164.6 164.6
4 C. McCoy TEXAS 163.0 173.8 -10.8
5 G. Harrell TTU 162.7 160.0 2.7
6 Z. Robinson OKST 155.8 166.8 -11.0
7 J. Ganz NEB 153.4 153.7 -0.3
8 M. Stafford UGA 150.6 153.5 -3.0
9 B. Johnson UTAH 148.4 149.4 -1.0
10 C. Daniel MIZZ 146.7 159.4 -12.7

Bradford’s and Sanchez’s numbers didn’t change much because Oklahoma played only one cupcake (I-AA Chattanooga) and USC didn’t play any.

You can see, however, that three of the other five Big 12 quarterbacks and Tebow benefited some from feasting on weaker, non-conference competition. At least in Tebow’s case he didn’t fall behind anyone as a result. No one else changed that dramatically, though Texas Tech’s Graham Harrell somehow got better against better competition.

Philip Rivers moves up into seventh place now that we’ve focused on quarterbacks from the top of Div. I-A and only how they do against other top teams. The college quarterbacks still have crappy BCS conference teams on their side, but at least the empty calories have been removed.

Finally, let’s take a look at the passer ratings of the college players.

Adjusted College Passer Ratings

This table contains the same guys, only this time it’s using the NFL’s system.

Top QBs from Power Teams Against Power Teams
Rank Player Team Pass. Rat. Adj. Pass. Rat. Diff.
1 S. Bradford OU 126.8 127.0 1
2 T. Tebow UF 117.6 122.1 -4.5
3 G. Harrell TTU 115.9 112.9 3.0
4 M. Sanchez USC 113.0 113.0
5 C. McCoy TEXAS 112.0 121.6 -9.6
6 J. Ganz NEB 103.8 103.0 0.9
7 B. Johnson UTAH 103.2 103.5 -0.3
8 Z. Robinson OKST 103.0 110.2 -7.2
9 M. Stafford UGA 98.5 101.7 -3.2
10 C. Daniel MIZZ 97.2 107.5 -10.3

So Peyton’s record is still falling at the hands of the new Heisman winner, but no one else is breaking it this year. Philip Rivers also moves up a spot to sixth, behind only the three Heisman finalists, USC’s new blue chipper, and a guy who runs an offense called the “Air Raid.” Not bad, Phil.

Missouri’s Chase Daniel again takes a hard hit in the rankings. This is no surprise to readers of the excellent Dr. Saturday site, where editor Matt Hinton showed that Daniel was only able to light up bad defenses this past season. Maybe it was the thumb injury, or maybe he wasn’t that good. I don’t know if we’ll ever find out.

Even as Daniel struggled to post big numbers against teams with a pulse, his adjusted passer rating was still higher than 30 of the 32 regular starting NFL quarterbacks. Why are there so many college quarterbacks with monster passer ratings?

Think Spectrums

I don’t mean to keep singling out Mike Hartline; I promise I have nothing against him. He just happened to finish exactly 100th in passing efficiency, so that got him chosen as the representative for the bottom of the college football quarterback pecking order.

His adjusted passing efficiency is 97.6, and his adjusted passer rating is 62.3. The former is higher than the efficiency for the NFL’s worst regular, Derek Anderson, but the latter is lower than the former Oregon State turnover machine’s rating. In other words, they are about even when it comes to performance relative to their rankings within their respective leagues.

That is why there are a lot of college guys at the top of the hypothetical combined rankings. There would be a lot at the bottom of them too, and plenty in the middle as well. After all, there are 119 teams in Div. I-A but only 32 NFL teams.

Quarterbacking quality is a spectrum, and college football simply has more guys to put on its range than the NFL does.

My goal wasn’t to try to tell you that college quarterbacks are better than pro quarterbacks because, as I said at the beginning, that’s patently untrue. I only wanted to show how the two major systems of rating quarterbacks compare so you can have some sort of reference when seeing one or the other.

Neither method is perfect, and there might even be a better one out there. Until you can convince the NFL or NCAA to adopt it though, passer rating and passing efficiency the big ones we’ve all got.

Now, at least, you can eyeball the differences in them and make a pretty good guess as to how college and pro quarterbacks are doing relative to each other and their respective leagues.