Very nice post 1992casey, just had to comment on this. Groundball pitchers tend to have higher than normal BABIP, flyball pitchers have lower than normal. GB tend to lead to more hits, FB to more outs. FB tend to lead to more extra base hits, GB more singles. Being a GB pitcher will increase your BABIP and WHIP but will lower your ERA in the long run. Also the more runners a pitcher puts on base the more random ERA becomes. Defense, LOB% and BABIP fluctuate a lot more when hitters are getting on more and when they are putting more balls in play. This is why stud pitchers tend to have pretty stable ERA year to year but the Dave Bush, Jason Marquis types fluctuate a lot. GB pitchers also tend to be a little more consistent because extra base hits can really mess with ERA over small samples.