When you factor in his 13 strikeouts, it's possibly the second most impressive game ever pitched in the history of baseball.

I don't know if you're familiar with the work of Bill James. To call him a statistician would be greatly oversimplfying, but basically that's what he is.

He was really the first guy to understand the importance of on base percentage, and he did a lot of work in figuring out how to determine things like the affect of the park on hitter's statistics, how minor league stats would project to the majors, etc.

Anyway, one of the statistics he developed was something called "Pitcher's Games Scores", a way to compare one pitching performance vs. another by assigning numerical values to to the factors that go into a pitcher's performance.

The goal was to develop a scale based on 100, so you could look at a pitcher's line in a boxscore, compute his game score, and have an idea, on a scale of 1-100, about how good his game was compared to others. He wanted an average game to be about 50, a great game to approach 100, and a terrible game to approach 0.

The formula he came up with was as follows:

Start with 50
Add one point for every batter the pitcher retires
Add two points for each inning the pitcher completes after the fourth inning
Add one point for each strikeout
Subtract one point for each walk
Subtract two points for each hit
Subtract four points for each earned run allowed
Subtract two points for each unearned run allowed

Based on the above, Johnson's game score last night was 100, right on the button.

Sandy Koufax pitched a perfect game in 1965 with 14 strikeouts, for a game score of 101.

Although it's possible to exceed 100 if you pitch into extra innings, my guess is that these two games are the only time ever that a pitcher has hit 100 in nine innings.