I have never seen anyone keep this stat, but I would like to see batting avg., slugging and on-base avg. for pitchers AFTER they put men on base.
I see so many pitchers who are mechanically well trained who simply cannot keep their composure and perform once a few little things go wrong.
I like a guy who doesn't panic if the leadoff man gets a double, or perhaps even a better test, a 2-base error. Because I don't care who you are or how much stuff you've got, you have to deal with these things to succeed. Can you keep that run from scoring? Can you clamp a bad inning with only 1-2 runs, or does the coach have to come get you because you come unglued?
Most folks judge these things subjectively. I suppose in the end at high levels it all comes out in the ERA wash in the long run. But as you are evaluating young pitchers in teen travel and high school ball, you will often see a kid on a bad team who shows some real bulldog tendencies.