Interesting. It appears his BABIP is fueled by his rather extreme FB tendencies: 47% this year compared to 34% league average. He's also been above average at getting infield fly balls (5% better this year). He's right at average for HR/FB, meaning the difference probably isn't his ability to stay in the ballpark in general. In fact, due to his FB tendencies, we'd expect greater than average HR allowed, a bad combination when combined with high BB's. You would think the walks and HR's would more than compensate for the fact that fly balls turn into outs at the highest rate (Low BABIP). Something other than pop ups and K's are keeping those walks from scoring apparently. New hypothesis: Santiago gives up a disproportionate amount of solo home runs, attacking hitters with no one on base. Santiago then picks when a runner gets on, looking for the pop up or strike out. He's good at getting both. His high pitch counts and short outings indicate picking. Basically, he'd rather walk in a run than give up a grand slam. Which is fine as long as he doesn't walk in a run then give up a grand slam. So you would look at total baserunners/9ip and multiply by HR/9ip, and that would be the expected amount of runs plated HR's. Then compare with the actual number of runs plated by the HR to remove even more luck out of the equation (premise whether a ball is caught or HR is somewhat luck). Then look for trends to see if a pitcher has a skill of avoiding more damaging HR or is more or less lucky. I get most of this would be within expected ranges for normal calculation of FIP, but for situations where you're looking at potential outliers, figuring out where the missing runs have gone (or in Nolasco's case, where extra runs came from) could be a useful tool .