I don’t want to make myself out to be smarter than I am, but here’s what I wrote last August:

It's just like the Cubs to get a good year out of someone, and assume a new permanent level of performance, but it rarely works out that way.

I don't feel very good about Dempster going forward. I'd just as soon they let him walk in the offseason.

Well, of course, as we all know, they didn’t let him walk, and instead signed him to a ridiculous extension.

So now we’re supposed to believe that Dempster is simply having a rough year, merely struggling with the mental aspect of his game. But I think we’re seeing something different; we’re seeing a pitcher have one good year, and then revert back to what his track record suggested he would be.

Even last season, Dempster was a pitcher who put too many men on base to be a really dominant reliever. The good news was that he didn’t allow very many homers, only 4 in 92 innings, kicked up his strikeout rate by over a man per inning, and he induced ground balls at roughly twice his usual rate. It was a good season, but it was all based on things that he had never done before.

This year, we’ve seen some of those gains slip away. He’s already allowed 3 homers in 35.2 IP, or at about twice the rate that he allowed last season. His strikeout rate has dipped, too, from 8.71 K/9 to 8.33 K/9. I’ll note that both of those numbers are still better than his career rates, but again, Dempster allows a lot of baserunners. When his escape mechanisms falter even a bit, it shows. And while he’s actually allowing slightly fewer baserunners this year than he did last year (mainly due to a decreased walk rate, of all things), it’s not been enough.

The biggest change, though, is that Dempster has once again become a flyball pitcher. Whatever he did last year to get so many grounders, he’s been unable to duplicate, as his GB/FB ratio has been cut in half (to 1.14) and is now in line with what it was when he was still a starter. What this suggests to me is that, while Dempster probably has become more effective as a reliever – a common phenomenon - he’s still essentially the same pitcher that he always was.

The bottom line is that track records matter. He’s simply too inconsistent to pitch a lot of high-leverage innings out of the bullpen. Unfortunately, even though this was fairly predictable, the Cubs will be paying for that inconsistency for much too long.