This headline reflects an assumption - pitchers in the WBC aren't at full strength. The rules and performance seem to agree, though. As does the PITCHf/x data.
Fourteen pitchers have appeared in the WBC in Toronto that also pitched at least once in Toronto during the 2008 season. Peak speed was found by taking the three fastest pitches from each pitcher's WBC games and comparing those to the three fastest pitches from that same pitcher's first 2008 game in Toronto.
This seemed like a quick-and-dirty-yet-reasonable way to see if anyone was throwing full speed. Yes, that's one game (2008) vs. one or more games (2009). Yes, Toronto's PITCHf/x may be different now than it was back then.
Every pitcher in the sample threw with less peak velocity during the Classic. K-Rod was down in velocity for most of 2008, so the fact that he's almost level doesn't mean he's closer to full speed.
Since half of the pitchers in the sample had more than one game in Toronto last season, we can add another wrinkle to the data. Here is the same chart, but using the latest game from 2008 when applicable.
Pretty much the same thing - K-Rod goes to the other side, saying his later Toronto appearance was deeper into this slow period.
WBC games move to Miami and San Diego this weekend, so we'll have more data to play with. I'll look and see if the park-to-park data shows a similar effect - I would expect the range to begin shifting towards less negative, or even positive, numbers.