It's safe to say that it's been a disappointing season for Starlin Castro. 82 games into the season, Castro's -1.4 fWAR makes Jeff Francoeur look like a valuable major league player (J.C. Bradbury nods approvingly). What is so different this year? MB posited to me a few weeks ago that pitchers have been pitching differently to him this year, and the numbers seem to bear it out.
For the last two seasons, the pitch mix that Castro had seen was fairly steady – roughly 32% four seamers, 21% two-seamers/sinkers, 20% sliders, and 10% curveballs (plus smaller amounts of less usual pitches). This year he's seen a lot more fastballs, with four-seamers going up to 38% and two-seamers/sinkers to 25%, a swing of about 10 points. While Castro has had about average results against sinking pitches, he's been awful against fastballs. In 2011-2012, Castro posted a .311 BA and .472 SLG against four seamers. This year it's .223/.311, with zero HRs. It looks like it's mostly due to contact issues – previously in his career he fouled off 48% of pitches he swung at and whiffed on 14%. This year, his foul rate has climbed to 53% and he's whiffing 18% of the time, for a total of 71% of negative to negative-ish outcomes when he swings. On average, he's not facing 'better' fastballs: the average velocity he's seeing is right around 92, which was also the average last year.
Plate discipline-wise, there hasn't been any significant change. The Cubs coaching staff has been trying to change Castro's approach, getting him to take more pitches early in the count and from what quotes I remember there's been some progress there. It's not really showing up in the plate discipline numbers though (and certainly not in his slash line). His in-zone and out of zone swing percentages are right in line with his career averages, and pitchers are throwing about as many strikes as in the past as well. The only significant differences that I see are a dip in his in-zone contact percentage (not surprising, given the fastball numbers above) and a drop in first-pitch strikes thrown by opposing pitchers.
Castro's batted ball percentages aren't too far off from what is normal for him. There's a slight dip in line drives and a rise in fly balls. His results on grounders and liners have been about the same, but he's seen a huge drop in performance on fly balls. Castro hit .300, .311, and .370 on fly balls the last three seasons. This year, it's .239. Maybe some balls aren't dropping in, I'm not sure. But that's a crazy low number. I can't remember if fangraphs includes popups with fly balls in those numbers, but even if they did his popup rate isn't particularly high this year.
Proportionally speaking, Castro has faced more left handed pitching than any other season of his career (26% of PAs are agaisnt lefties). However, as MO pointed out the other day, Castro has been strangely dreadful against lefties, posting a .213 wOBA when he was regularly posting an average of .360 or so earlier in his career. He's getting about 43% fastballs from LHP, and given his struggles against fastballs this year that could be part of the cause. He's hitting poorly against all types of pitches from lefties this year, while in the past he crushed lefy fastballs, sinkers, and changeups. He still has a .154 ISO against lefty changeups this year, but overall he's making poor contact.
Like other noted bloggers around the Cubs-o-sphere, I'm no hitting coach so I have no idea how Castro of the Cubs coaching staff should make these adjustments. But if I had to pick one thing, it would be whatever is up with his contact rate.