In an era where baseball fans are suffering from statistical overload, the last thing we need is one more stat, right? Well, perhaps that’s the case, but not if the stat can improve upon already existing stats, which is my goal with the pitching efficiency rating (PER).
The purpose of PER is to grade a pitching performance (right now, I’m only using it to grade starters, it will need some tweaks in order to properly evaluate relievers). Currently, the most common stats used to evaluate statistics are Game Score and Quality Start.
I see no use for the stat “quality start.” As many have pointed out before me: what is quality about six innings and three runs? That’s an ERA of 4.50 – an ERA which is roughly in line with the career numbers of Russ Springer, Scott Kamienecki, Omar Daal and many other less-than-quality pitchers.
As for Game Score, I think it has its use, but it should not be the standard grade of a pitching performance. Game score is more of a pitching dominance measurement. For example, in 2009 Mark Buehrle’s perfect game was tied with Chris Carpenter’s one-hit, two-walk shutout for the second best Game Score of the year. Both were fine performances, but Buehrle’s was certainly more impressive – or at the very least, more efficient.
Which leads me to my new evaluation tool: PER
PER uses three components:
Percent of Batters Retired: (IP*3)/((IP*3)+Hits+Walks+HBP)
Technically this isn’t an exact percentage. It removes errors from the equation in order to attempt to neutralize the main factor which is out of the pitcher’s control. The (IP*3) portion of the equation generates the number of batters the pitcher should have faced, had his defense held up behind him. For example, if a pitcher throws a 7 innings, allowing 3 hit, 2 walks, and 1 HBP his equation would look like this:
Percent of Batters Failing to Score: 1-(ER/BF)
This portion of the formula is a little more straight forward. Only earned runs are included again to neutralize any poor defense of which the pitcher may be a victim.
Percent of Game Pitching: IP/9
A complete game gives a pitcher a full score in this category. I’m sure someone will be quick to point out that a pitcher doesn’t always have the opportunity to pitch nine innings. This is true, and it is a minor flaw in the formula. Unfortunately I haven’t found a way to account for this without manually going through 1,000s of box scores to determine if the pitcher tossed the full amount of innings. Also, I’m not sure if it would be fair to do that even if we could. If a pitcher has a perfect game through 5 innings and the game is called, should that really receive the same score as a nine-inning perfect game?
You may have noticed that each category will give you a number no greater than 1 (unless a pitcher throws more than nine innings). This allows us to add the three categories together and divide by three giving a score which, except for a few rare occasions, will be no greater than 1.00 – essentially looking like a batting average.
Now how does this formula look in practice? Here are the highest rated games from the 2009 season. Buehrle and Sanchez were each credited with a perfect game. The only batter to reach base in Sanchez’s no-hitter did so on an error.
PER can also be used to determine season leaders: