September 4, 2007

Quality Starts

During last night's game, I said I thought Matsuzaka was our #2 starter based on ERA+. Other people mentioned Quality Starts as a possible measuring stick.

OttoC at SoSH has a thread this morning that takes a quick look at this issue.
There has been some talk about Quality Starts on this list. There has been criticism -- 3 earned runs in 6 innings is equivalent to a 4.50 ERA; it only counts earned runs, not all runs. I've postulated in another thread that Quality Plus Starts (QS+) where the run criterion is reduced to two, or fewer runs in 6+ innings might prove a better metric.
OttoC looked at starting pitcher logs from 1957 to end of August 2007.
Quality Starts were recorded in about 51.5% of the games with the starter having a .736 winning percentage in them. ERA: 1.91. Avg IP: 7.56.

About 76% of the Quality Starts were Quality-plus Starts with the starter having a .792 winning percentage in them. ERA: 1.36. Avg IP: 7.67.

... although the Quality Start metric is frequently maligned, the numbers show that when a pitcher records one, it most often represents a very good start. So much so that my effort with Quality-plus Starts is not really needed.
Matsuzaka has 17 Quality Starts (15 of which would be QS+); for Beckett it's 13 of 16.


curt said...

I always thought that the QS definition, though it has the advantage of simplicity, was a bit too generous. 6 IP / 3 ER is not only a 4.50 ERA, but also places a 3 inning burden on the bullpen.

My proposal would be this: a Quality start is 7+ IP / 3- ER or 6+ IP / 2- ER. This would lower the minimum ERA to 3.86 and hold a shorter outing to a higher standard.

s1c said...

I have always used quality starts as a yard stick. While some people say it works out to a 4.5 era, that isn't the point. The quality start is at least six innings and three or less earned runs. That is a minimum and a maximum, you don't get a quality start if you go 9 innings and allow 4 or less. You have to have three or less.

So far this year the sox have had 74 QS in 138 games (54%), they have gone 7 or more innings in 37.7% games and average 6.20 innings per start.

The starters though have a 61.1 % winning percentage overall, with the Red Sox having the most wins by their starters in the majors.

So, quality starts are a tool, but like all tools, they should not be the only tool you use when evaluating players.