Mon Jan 30, 2017 11:43 pm
I look at from this standpoint -
The odds of rolling a CF(X) on any one play is 1.4%. Assuming you face 36 batters in a game (Min 27 + 9), the odds that any batter will hit CF(X) is 1.4%*36= 0.504 batters. Roundup and we can assume that 1 batter out of 36 will roll a CF(X).
Without the X-Charts handy, I will assume that 1-3 are hits for 2 CF, and 0 for a 1 CF. So there is 15% chance for a hit vs 0% chance. But also need to consider that the odds a runner can advance with less than 2 outs. A 2 CF allows more chances for advancement than a 1.
The other side of the equation is the arm. Each + adds 5% for advancing runners to be safe, each - reduces that chance by 5%. So a +3 arm adds 15% chance for an advancing runner to be safe. A 1-17 runner would have an 85% chance to advance against a zero arm OF. Against a +3 it is technically 100% (though I believe a 20 is always an out, so 95%). It allows a 1-10 runner who has a 50% chance to run normally, to advance with 65% chance of success.
So assuming 9 baserunners in a game, what chance does a hitter have to hit either FB to CF, or an open ended single to CF that would allow a chance for advancement. That is harder to calculate without a baseline of the average singles and FB to CF, but I would assume it to be more than 1 per 36 batters.
Even without the baseline, I would say the odds are that the arm will come into play more often in a game than a CF-X.