WBC to blame for Soria's injury?

Joakim Soria's on the DL, and as the Kansas City Star's Sam Mellinger reports, Royals GM Dayton Moore thinks it might be the World Baseball Classic's fault. Soria

    "I don't think it helps,” Moore said. "We couldn't control his work. If you can't control a pitcher's workload and you can't script their preparation during spring training, it's a problem.”
    Soria pitched only two innings for Mexico in the WBC, missing 17 days of spring training. Moore makes the point that the primary reason spring training lasts as long as it does -- close to seven weeks this year -- is to ensure teams can best prepare their pitchers for opening day.

    Pitchers who participate in the WBC miss out on that, leaving them open to underperformance or injury. The numbers back that up.

    The Star analyzed 45 pitchers who threw at least 20 innings in the big leagues last year, participated in the WBC and have pitched this season.

    As a group, their ERA jumped from 3.79 last year to 4.58 so far this season. Across baseball, ERAs are up from an average of 4.32 to 4.51.

    Seven WBC pitchers are currently or have been on the disabled list already this season -- including five for arm or shoulder injuries.

    USA Today did a similar study on the pitchers from the 2006 WBC. It found that more than one in three spent time on the disabled list and that the group's ERA jumped from an average of 3.69 to 4.37. That's an 18.4 percent increase in a year when ERAs rose 5.6 percent.

These studies are interesting, and probably a necessary step toward figuring out how pitching in the WBC affects pitchers. But it seems to me just the first step (and a fairly simplistic step at that).
What sort of pitchers pitch in the WBC? Pitchers who did particularly well in the previous season.

What do pitchers who did particularly well in the previous season tend to do? Regress toward the mean. We would expect WBC pitchers' ERAs to increase from one season to the next.

Would we expect them to increase by 18 percent, as they did three years ago? We probably would not. But that's just one year and a fairly small group of pitchers.

Would we expect WBC pitchers' ERAs to increase by 21 percent, as they have this year? We would not. But that's just five weeks of a six-month season.

I do believe that Dayton Moore's concerns are legitimate, and I suspect that baseball people are conducting rigorous analyses that go a long way toward quantifying the impact of the WBC. I don't think we've seen those analyses yet, and perhaps we never will. But if you start reading about the clubs exerting some real pressure on Major League Baseball to make real changes, you can guess that it's informed by that internal analysis.