quality starts?

there's been some discussion about the value of the quality start. bruce miles, fred, and ssr have been kind enough to come up with some numbers on various things. we were discussing this in the game thread, but i'm moving it here since everyone is crazy there.

For no decisions Cubs starters(Z, Lilly, Hill, Marquis, Marshall) 4.45 ERA

 

1.84 ERA in wins.

 

7.39 in losses.

Now that Trachsel's line is in the books, the updated ERA on the Cubs' quality starts this year is 1.78. It was only the third quality start this year for the Cubs in which a pitcher has met only the minimum requirement (6 innings and no more than 3 earned runs). Given the Cubs' record, the overall ERA in quality starts and the record when they don't get one, I'd say the quality start, although not perfect, is a pretty good measuring stick.

so what do we make of all this? i say that this shows that quality starts is a reasonable proxy for how well a pitcher has done, but then so is wins and losses. both qs and w-l will usually get the general picture right, but will also have some major blind spots, with w-l's blind spots likely being more significant. in the end, there's probably not much reason to use either stat since we have access to much better metrics.

anyone else have an alternative analysis?