What's a Perfect Game?

Guest column by Pete Palmer

The NFL passer rating has many faults, including the fact that nobody understands it. Other major problems include the 80-yard bonus for touchdowns, the 100-yard penalty for interceptions, and the 20-yard bonus for completions. A passer who completes two passes in two attempts for 0 yards gets a total of 40 yards credit, the same as another passer who completed one pass in two attempts for 20 yards. A 90-yard pass from the goal line to the opponents' 10 is worth 110 yards (90 plus the 20-yard bonus for the completion), the same as a 10-yard touchdown pass (10 plus 20, plus 80 for the score).

Of course, they didn't plan it that way, but that's the way it turned out.

The History of Rating Passers

From 1932 to 1937, passers were ranked simply by total yards passing; from 1938 to 1940, completion percentage was used.

In 1941, qualifying passers were ranked in four categories: completions; completion percentage; total yards; touchdown passes; interceptions; and interception percentage. Each passer's ranks were totaled, and the player with the lowest score won. This method was used until 1948. In 1949, the number of interceptions was dropped from the equation.

From 1950 to 1959, the NFL went simply with yards per pass.

In 1960 and 1961, they used a system similar to that used in 1941-49, but using six categories: total completions; total yards; total touchdowns; completion percentage; interception percentage; and average yards per attempt. In 1962, they used four categories, dropping total completions and total yards. That system lasted until 1972, when total touchdowns were dropped in favor of touchdown percentage.

The number of pass attempts needed to qualify for the passing title also changed through the years. In 1950 it took 100 attempts to qualify. This was raised to 10 attempts per game in 1960 and 14 attempts per game in the 1980s.

1973: The NFL Passer Rating Is Born

The current method, which debuted in 1973, was developed and tested over a three-year period by a committee headed by Don Smith of the Hall of Fame, and including Seymour Siwoff of Elias, Don Weiss of the NFL, Jan Van Duser, Curt Mosher, Tom Grimes, Bill McGrane and Jack Horrigan.

The rationale behind the new system was to calculate a rating that was independent of other passing stats and could be used to get a figure for non-qualifiers. They decided to give a value of 1.0 for average performance and 2.0 for record performance. These two points were then used to find the value for 0.0. Any value below zero would be rated at zero, so there were no negative ratings.

In addition, an absolute maximum rate of 2.375 in each category was established. Why 2.375? That's what a passer would score for interception percentage if he never threw a pick. Since that was the maximum score for interception percentage, they applied the same cap to all categories across the board.

Since this was established in the days before computers were generally available, the league published a booklet with tables that contained the values for each item. To get the final rating, you would add up the four components and check the fifth table, which simply divided the number by six and multiplied it by 100, converting it to a percentage. Since average performance would give you a 1.0 rating in each category, the average overall rating was 66.7. The current average has increased to about 80.0 today, due to the refinement of the passing game.

A player who hit the 2.375 cap in all four categories would have a rating of 158.3, the highest score possible. Here is the complete list of the NFL's perfect games, using the current system. Rate1 is the normal NFL method, while Rate2 will be discussed later:

Problems With The System

The biggest problem with this system was mentioned earlier: Almost nobody understands it, and those who do still find it awkward to use.

Another problem with this system is that the limits for each component make it so stats above or below certain values have no effect. The limits are shown in the table above. These work fairly well for season stats, although Sid Luckman got cheated out of the all-time rating record because in 1943 his touchdown percentage was 13.9%, but he only got credit for 11.875%. His rating should have been 114.2, not 107.6, and it would have been his record that Peyton Manning broke in 2004, not Steve Young's. More importantly, the rate caps make this a poor method of measuring individual games.

With a little algebra, you can convert the rating formula into yards, with bonuses and penalties for various events. Rate A below is the adjusted yard value, while Rate B shows the conversion to a percentage.

Rate A = (Yards + Comp x 20 + TD x 80 - Int x 100) / Att
Rate B = 100/24 x Rate A + 50/24

Tom Brady scored a perfect 158.3 "true" rating for the Miami game last year, but his rating would have been 211.1 if you eliminate the arbitrary maximums. There have been 20 games with a 158.3 NFL rating in league history. If we remove rate caps, that figure has been matched or exceeded 124 times, but only Johnny Unitas in 1967 vs. Atlanta had a better figure than Brady. Atlanta was an expansion team in their second year. Under the no-limits system, Brady had three 150-plus games in 2007, tying him with Steve Young in 1993. Brady's career mark of six such game ties him at second with Young and Kurt Warner, behind Peyton Manning's seven.

The table below shows the top 20 passing games from 1950 to date, using the no-limits system. A minimum of 20 attempts was required. Again, Rate1 is the normal NFL method, while Rate2 eliminates the limits. Only five of these passers scored a maximum 158.3 rating using the NFL method:

A New System

I would propose a similar system to the no-limits formula; however, the bonuses and penalties would be changed. The completion bonus would be eliminated, the touchdown bonus would be changed to 10 yards and the interception penalty reduced to 40 yards. These are consistent with the actual values of the plays. If a passer goes 90 yards downfield in 10 pass attempts, it really does not matter if he had four completions or six, or even one. The average number of points scored from a first-and-goal on the 1-yard line is about 6, not 7, so the last yard is the hardest to gain and there should be a bonus for crossing that threshold. It normally takes about 12 yards to put one point on the scoreboard, but here it is only 1, so a bonus of 10 is about right. A turnover on the spot is worth about 50 yards. However, the passer gets no credit for the length of the intercepted pass and the return is usually short, often zero.

Also, there would no arbitrary limits to any of these values.

Since the improved method emphasizes yards per pass, while the old method stresses completion percentage, there is not much crossover between the two lists above and the top 20 using the new method. Only four of those on the 158.3 list show up again, and only 10 from the no-limits list. Rate3 is the new method, expressed in adjusted yards per attempt. Johnny U still leads, but Brady drops down to No. 12. Joe Namath comes in second, thanks to his extremely high average gain, which even overcomes his interception. The players shown below have a much broader historical range than the previous lists, with almost half going back before 1980, even though there were fewer teams and fewer games. Passing then was less concerned with the short possession game.

Pete Palmer is one of the original co-authors of The Hidden Game of Baseball and The Hidden Game of Football, and currently serves as one of the co-editors of the ESPN Pro Football Encyclopedia.