The biggest rally killer in BB is the DP. FIP, xFIP, WAR or any other sabermetric stat can never tell you how a group of 4 infielders will do. They each have to have absolute belief that each will do the job needed to pull it off. It will then reflect on the pitching staff. An infield D that pulls off DPs really well tends to also develop a pitching staff to throw for ground balls. On the otherhand if the infield does not have the trust to pull off the DP, you then will see a pitching staff that will then try for the strikeout or flyball. All this gets reflected in ERA and WHIP.
Sabermetrics can never tell you that story. Sabermetrics is fun, but because I believe BB is a TEAM sport, the team individual part sabermetrics are important, sabermetrics sum total rarely tell you what the TEAM results will be.