The Mariners traded for Casey Kotchman and he will regain a full-time role there after playing just part-time in Boston. As Dave Cameron noted, this might be his last opportunity to show that he can hit enough to be a full-time MLB first basemen. That is not to say that he is ever going to be a big-slugging first baseman — even 20 HRs seems like a stretch — but maybe he can have doubles power and post a high enough BABIP to be an asset at the plate.
That was the case in 2007 when 37 doubles and a .308 BABIP coupled with his always good contact skills and plate discipline (over his career he has only slightly more strikeouts than walks) resulted in a solid 121 wRC+. Since then he has posted wRC+s in the 90s. Not bad, but not what you expect from a player at a position near the bottom of the defensive spectrum.
The problem has been with his balls in play, as both his ISO and BABIP have fallen since 2007. To dig deeper into the cause of this drop I wanted to look at his balls in play.
I use the same technique I introduced in my Garrett Atkins post, by breaking the field in ten zones and looking at the number of non-ground balls to each zone and the slugging on those balls (in the Atkins post I used BABIP, but here I use slugging). The first zone is the infield, and after that each ring is 100 feet from the pervious. So the three zones after the infield include balls in the air less than 100 feet beyond the infield-grass line. The number in each zone is the fraction of balls in the air to that zone. The color shows the slugging percentage on balls hit in the air in that zone. The lightest color (the infield for example) has a slugging of zero, and the darkest color (deep right field) has a slugging of about 2.5, so balls in the air to that zone result in a little bit more than a double, on average.
Clearly, Kotchman’s power is to to right field, as is typical for a LHB. But in 2007 he hit more balls, and with better results, to center field. The other major difference is in the number of balls in the air to the infield; he has had many more since 2007. These pop-ups are effectively automatic outs. Another slight difference is on the slugging on balls to left field just beyond the infield. In 2007, that was 0.778; but since, just 0.240. These are most likely bloop singles, and this difference is most likely just luck.
So the big differences are more power to center, a few more lucky bloop singles to left and fewer pop-ups in 2007. Whether he can regain 2007 is still an open question, but I think it is interesting to see that the performance in 2007 was a mix of performance (less pop-ups and more long hits to center) and luck (bloop singles). A last consideration is that, as Dave noted, Kotchman will be aided by the short right field walls in Safeco, where he hits a large proportion of his long flies.