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-P- Via Van Slyke, this article about Oliver Perez's mechanics is just fantastic.

-P- USA Today writes about the Pirates and the Royals' role as spoilers. After an indescribably miserable start, the Royals have quietly played almost .500 baseball for about their last 90 games.

-P- Here's the Post-Gazette's new Q+A. On the Pirates' supposed resurgence:

I am hearing from readers who cite the Pirates' meager run differential as evidence that what they are doing is a mirage. I understand the long-term relevance there, but I also know that there are tons of variables that go with that number just as there are tons of variables that go with wins and losses.

This seems like a blown opportunity. I wish someone in Pittsburgh's mainstream media would explain to Pirates fans why run differential is important - I know the Stats Geek has mentioned it a couple of times, but I don't think he's ever really explained it. (Somebody correct me if I'm wrong about that - and yes, I know about this column, which explains one-run wins and losses pretty well.)

There are certainly "tons of variables" in the factors behind both run differential and actual wins and losses, but to leave it at that misses something important, something that need not be surrounded by a fog of complexity - historically, teams that outperform or underperform their run differential tend to regress to the mean. Bill James showed that in the 1980s.

It's true that there are "tons of variables" that affect run differential, but those are basically the components of run scoring and run allowing (hits, walks, power and so on), park factors, and strength of schedule. Looking at the Pirates' numbers in those areas, there's no reason to think they've actually improved substantially in a way that isn't reflected by their run differential.

Freaky things do happen in short periods of time, or even over the course of an entire season. When these things happen to the Pirates, be they positive or negative, fans' opinions tend to change with them. I'm guilty of this to some extent too - although, in June, I did point out that the Pirates were not as bad as their record, for about the same reasons as I'm now saying that they haven't actually gotten better.

A good rule of thumb is when something is happening that baseball history says is unlikely to continue happening in the future, it's probably not likely to continue happening in the future. That sounds like a snarky thing to say, but I don't intend it to be. Outperforming one's run differential is not a skill - or is not a skill one can depend much on. If the Pirates are going to improve, their run differential is going to have to change.

Another thing here, too, is that if the Pirates ever get much better, it won't happen for no reason. It'll happen because they planned to get better and they brought in players in accordance with a coherent plan. The Pirates won't just get better out of nowhere, with approximately the same mix of players they had (minus some veterans) when they were horrible at the beginning of this year. They'll get better when they get a plan and get some better players. And, by extension, they'll get a plan when they get a better general manager. And, by extension, they'll get a better general manager when they get better owners. It may not happen exactly like that, but the Pirates probably won't get better when a group of mediocre players suddenly congeals into something better. They'll really improve when they get some players who aren't mediocre.

I'm probably rambling and being unclear here, but the point is that you shouldn't trust a half-season's worth of games if there's no compelling reason to do so, and you especially shouldn't trust it if there's an extremely compelling reason not to do so. This is true of single players, and it's just as true of a franchise that has a pretty lengthy recent history of shooting itself in the foot over and over again.

Anyway, elsewhere in the Q+A, we learn that the Rockies wanted only John Grabow and a prospect for Ryan Shealy. Unless the prospect was Andrew McCutchen, Neil Walker or Brent Lillibridge, I can't understand not taking that deal.