That link will give you more detail on what Jeff did, but the basics are this: He incorporated two new pieces of informatoin into the calculation. One is "hard contact" data from Inside Edge. They categorize every ball in play as Weak, Medium or Hard hit and Jeff found the not-so-surprising connection between hard contact and balls finding holes. He also incorporated Bill James' Speed Score, since being fast also leads to more hits on balls in play.
The chart below combines what I shared last week with the same data based on Jeff's new equation.
Some quick definitions - BBType is xBABIP based on batted ball type while HH/Spd is xBABIP including hard hit and speed score data. They each have a diff column showing how much higher the xBABIP is than the actual (so positive means the hitter had bad luck). xDiff is the difference between the two formulas for each player.
The first thing to note is that 11 of the 12 player we looked at had lower xBABIPs once you account for hard hit and speed. There are three possible explanations for this:
1. The new formula just plain returns lower numbers for all players. This, in fact, turns out to be true. Using the batted ball type formula, I found a 2014 league average xBABIP of .305, while based on the chart in this article, 2014 league average xBABIP was .296. That, though, does not explain everything. Even if we decrease all the Indians xBABIPs from the old calculation by .009, we have 11 of 12 seeing their xBABIPs go down even further. So what other explanations are there?
2. Indians players are all slow and therefore, once we account for speed, we expect lower BABIPs. This seems a bit unlikely. First of all, the calculation for speed score includes things like stolen bases (Cleveland was 10th in MLB last year) and triples (Indians were 23rd). Stolen base percentage also factors in, and the Indians were very strong in that department. This certainly helps to explain why Nick Swisher had such a big gap, though. It probably is not super informative on Michael Bourn, though.
3. Indians players hit the ball hard rarely. Maybe this is the Bourn explanation? The one player who had a higher xBABIP with the new formula is Brandon Moss, who definitely hits hard. Carlos Santana and Yan Gomes also tend to strike the ball solidly, and they were the next closest in xBABIP scores.