I'm working on a Q+A for Pittsburgh Sports Daily Bulletin. (It'll probably be available later this week, but they asked a lot of questions, so it'll take a day or so for me to finish it.) One of the questions they asked was which Pirates might surprise fans this year. You could interpret "surprise" to mean a lot of things, of course, but here are a few players who I think could have pleasantly surprising seasons.
-P- Charlie Morton. There's nowhere to go but up, really. Morton's track record is so sketchy at this point that it's extremely unlikely that he'll ever be the ace he sometimes looks like, but with his stuff and his Class AAA success in 2008 and 2009 and his modest success in the majors in '09, he could re-emerge as a middle-of-the-rotation starter. That probably wouldn't shock many Bucs Dugout readers, but I think a lot of other fans would be surprised. He's out of options, and the Pirates are clearly still pretty curious about him, so he has a very good shot at winning the last rotation job.
-P- James McDonald. This one is a little bit strange, since McDonald was so good last year. But his 2010 line could have been even better if John Russell hadn't repeatedly hung him out to dry. McDonald began most games looking like a Cy Young contender, but his stuff deteriorated rapidly after 45 pitches or so, and then he would get pasted. (He had a .627 OPS against in pitches 31-45 of his starts and a 1.026 OPS against in pitches 45-60. He calmed down a bit in pitches 61-75, so sample-size issues probably explain to some degree why McDonald was so bad from 45-60, but still - the decline in his stuff as games went on was undeniable. See update below.)
I can't believe the Pirates aren't aware of this problem. In PirateFest, Clint Hurdle spoke about how he wanted to preserve the Pirates' bullpen by having starters pitch deep into games, but hopefully he'll be able to rely on Paul Maholm and Ross Ohlendorf to pitch the longer outings. Unfortunately, Kevin Correia has a problem similar to McDonald in that he started to get rocked after about 45 pitches last year, and Ohlendorf wasn't exactly a model of durability in 2010. But this is where the Pirates' pitching depth could come in handy, as Scott Olsen and Jeff Karstens can both pitch long relief stints (assuming both are in the bullpen).
Ultimately, of course, McDonald needs to do a better job preserving his stuff deep into games. If he can't last more than 45 pitches more consistently, he can't be much of a starter in the long term. But if he can improve on that somewhat this year while also being used a little more intelligently, he could have a special season.
UPDATE: Well, check that. I was using ESPN's splits data, which appear to match Baseball Reference's, except that the numbers for BB-Ref's are for pitches 1-25, 26-50, 51-75, 76-100 and beyond 100. So the numbers for pitches 76-100 at BB-ref match the numbers for pitches for 46-60 at ESPN. BB-Ref's numbers make more sense (I was wondering why ESPN didn't have any numbers beyond 75 pitches), so those are probably accurate, which means that the big decline is after 75 pitches, not 45.
You can also check out McDonald's inning-by-inning splits at the same page at BB-Ref - that might resolve some of the confusion. Essentially, he did well through the first three innings, and then there was a pretty steep rise in OPS against after the third inning and a decline in his peripherals after the fourth or fifth. There are some issues with sample size, and it's not necessarily unusual for pitchers to struggle through the middle innings at times, but the decline appears to have come later for McDonald than I indicated up above. Still, it certainly would have helped his overall numbers if Russell hadn't been leaving him out there when he was plainly gassed.
-P- Rudy Owens. Owens probably won't make the team out of Spring Training or anything, but he's so polished that he could be surprisingly successful right away. The Pirates' ownership loves him, and if Zach Duke could blow through the league in his rookie season, I see no reason Owens can't.
Another potential surprise candidate might be Chris Resop, who could emerge as one of the National League's better setup men this year.
You'll notice I didn't put any of the Pirates' young hitters here. That's because, in the cases of Neil Walker and Jose Tabata, they were already surprisingly good last year, or because, in the cases of Andrew McCutchen and Pedro Alvarez, it's hard to believe they'd take anyone by surprise even if they broke out in a big way.