This is based on nearly 1,000 cases since 1999. Essentially it's baserunners per nine rankings of pitchers with at least 150 innings in that season and the correlation to their ERA. I included pitchers with at least 40 innings thus far this year to get closer to 1,000. What the correlation shows us is that this can tell us to a pretty decent degree what an ERA SHOULD be.
For those a bit unfamiliar with how to plug the numbers in just follow the formula at the top right of the image [.4902*(baserunners9) - 1.7145] and we'll get a "projected ERA". Amongst those whose ERAs have been amongst the most lucky this year: Edinson Volquez (projected ERA 3.85), Fausto Carmona (4.9), Tim Lincecum (3.84), Daisuke Matsuzaka (3.76), and John Lannan (5.14). The unlucky ones include Johnny Cueto (3.58), Dave Bush (4.53), Ted Lilly (3.95), Justin Verlander (4.78), and Jarrod Washburn (4.32).
If you're an owner of Volquez and you need another position, it would be smart to cash in now. He's not going to erupt, but that sparkling ERA is going to go away sooner than later.