Inspired by Low Country Joe's odd devotion to Quality Starts -- I decided to study the issue, based on the premise of Quality Starts, but using a worthwhile measure.

The measure is based on the odds of winning when a team gives up a given number of runs:

According to Baseball Prospectus and using my math, here is the league's winning percentage with each score allowed:

RA Winning %
0 100%
1 91%
2 79%
3 69%
4 53%
5 43%
6 31%
7 22%
8 18%
9 11%
10 6%
11+ 0%*

* 11+ is not actually 0, but for simplicity and due to my desire not to give a pitcher points for giving up that many runs, I set it at 0.

Now the key measure is what I call "Team Runs". The formula to calculate this is ER+(9-IP)*4.5, rounded in the mathematically appropriate direction for individual games.

So if a pitcher gave up 3 runs through 6 innings, Team Runs for the game would be 5. 5 runs gives a team a 43% chance of winning, so the pitcher gets 43 points for the game.

Then you just average the score for each game and you get the percentage of games that a pitcher would win with an average bullpen, an average offense and average luck.

Simple enough? I think so. Here are the results for select pitchers:

Santana 62.82
Oswalt 61.30
Carpenter 60.53
Halladay 59.97
Webb 59.24
Zito 55.47
Capuano 52.56
Haren 51.94
Millwood 49.76
Blanton 46.72
Loaiza 46.58

Alternately, using SalB's Pythagorean model, we get:

Santana 65.79
Carpenter 64.61
Oswalt 64.33
Webb 63.87
Halladay 63.07
Zito 59.78
Haren 56.55
Millwood 53.53
Blanton 51.01
Loaiza 50.99