When it comes to hitting for contact, Chris Carter is pretty definitively the worst in the league right now. If we usual a literal interpretation of the hit tool and say that it indeed relates to specifically the statistic of batting average, Carter could be heading for the basement if his BABIP regresses to something more in line with his profile. Whichever way you slice it he is the very deserving winner of the final "MLB's Worst Tools" award. I'm sure it will adorn the mantlepiece of the of the Carter household for centuries to come.
In certain unofficial calculations, the denominator is simplified and replaced by Plate Appearance (PA); however, the calculation PAs includes certain infrequent events that will slightly lower the calculated OBP (i.e. catcher's interference, and sacrifice bunts). Sacrifice bunts are excluded from consideration on the basis that they are usually imposed by the manager with the expectation that the batter will not reach base, and thus do not accurately reflect the batter's ability to reach base when attempting to do so.
On base percentage (OBP) or on base average (OBA) is an important component in a sabermetrics styled view of offensive productivity, but it is by no means the ultimate statistic to measure a hitter’s value. Unlike AVG and SLG, OBP does take walks into account, but it gives the same weight to a home run as it does to a single or a walk. Obviously, those are events in a baseball game that don’t have the same value in terms of producing runs. Billy Beane was quoted once as saying that OBA is three times as important as SLG. Well, is it? Not from a sabermetrics view point. Sabermetrics isn’t based on money at all. Bill James and the folks that blazed the trail for the development of sabermetrics certainly know that a home run has more value than a walk. It just so happens that players that had an ability to get on base were not paid as well as some of those who racked up RBIs. Obviously, the players who do it all get paid the most.