Most years, it seems that the Pirates are about average in either runs scored or runs allowed and dramatically below average on the other. This can lead fans to argue that if they only spent some money on players to help on the side of the ball where they'd been lacking, they'd suddenly have an above-average team.
The Pirates' offense, led by a resurgent Jason Bay and somewhat surprising years from Xavier Nady, Nate McLouth and Ryan Doumit, hit well for the first few months of 2008 despite receiving little help from Adam LaRoche or Freddy Sanchez. You might think that the Pirates could have sculpted an offensive core like that into a winning team by adding a couple of decent pitchers, but you'd be wrong.
Leaving aside that the offense was merely mediocre anyway and was running entirely on McLouth and three players with extensive injury histories, the real problem was that the Pirates' position players were a big part of what appeared to be problems with their pitching. The Pirates' pitching this year was bad but not nearly as terrible as it seemed, and adding new pitching to the mix was unlikely to help this group much because nearly any new pitcher would've instantly looked worse with the Pirates' defense behind him.
As I write this, the Pirates' defensive efficiency is .679, the worst in the majors. In 2007, it was .676, third worst in the majors, with many of the same key defensive players. In 2006, it was .676, worst in the majors. Defensive efficiency isn't some fancy statistic; it simply measures the rate at which balls in play are converted into outs. The Pirates are awful at it, and they have been for some time. Assigning blame to individual players for this is difficult and debatable, but it's probably less important to do that than to simply acknowledge that this isn't a mediocre defense we're looking at, it's a horrible one. Also, the core of position players with which the PIrates started the season was unlikely to get much better--both middle infielders (Sanchez and Jack Wilson) were entering their thirties, and none of the other starters were particularly young.
The Pirates' defense might have improved some if everyone could have stayed healthy at the same time, but that would have been unlikely, and actually the Pirates were somewhat lucky this year that their regular players stayed as healthy as they did. So to be halfway decent at run prevention with the core of position players they had, the Pirates would have had to bring in some extraordinary pitchers.
Among all pitchers who have thrown at least 100 innings this year, Paul Maholm places 33rd of 142 in batting average on balls in play (BABIP) with .273. Tom Gorzelanny places 69th, with .287. Zach Duke is 128th, with .311. And Ian Snell ranks 141st with .338. So Maholm was solidly above average in this category (this, unfortunately, explains away a big part of his breakout year), Gorzelanny was about average, Duke was awful, and Snell was beyond awful.
Pitchers have very little to do with their BABIP. That's mostly on the defense, and for the Pirates' starters, the defense simply did not get the job done. Snell didn't have a good year by any standard, but his defense completely failed him. Snell could have lopped a run off his ERA if he'd had an average defense behind him.
Zach Duke simply is not a bad pitcher and was not an important part of the 2008 Pirates' problems. Obviously, he's not the pitcher he was when he came up in 2005, but it's no coincidence that was the last year the Pirates had a semi-competent defense. If the Pirates had had their 2008 defense in 2005 and their 2005 defense in 2008, Duke would now look like a reliable rotation cog, not a disappointment.
The Pirates' defense has simply destroyed Duke the past three years. As a pitch-to-contact starter, Duke not only has dealt with ridiculous BABIPs, but those BABIPs have harmed him greatly because batters put the ball in play so often against him. In addition to finishing near the bottom in BABIP this year, Duke was dead last in 2007 and 123rd of 138 in 2006.
As with any team, the Pirates' pitchers' fortunes are closely tied to the performance of their defense. As well as the Pirates hit at times this year, it would have been very difficult to generate better overall results with the same core of position players, because their defense would have continued to eat pitchers alive.
This is one reason why the Pirates can't find their own Kyle Lohse. Put Kyle Lohse on the Pirates, and he probably won't look very good, whether or not he actually pitches well. It's not really about an inability to find good pitching. It's about defense, and the Pirates didn't have it.