MLB.com's year-end wrap-up of the Pirates' 2005 season is a case study in why you shouldn't assume that everything will go right before a season starts. Ed Eagle claims that the Pirates were "cautiously optimistic" that the team could finish at .500 or better before the season started, but that injuries did them in.
The fact is that the 2005 Pirates spent about an average number of days on the disabled list. Oliver Perez' ineffectiveness, which was probably partly due to his health, was predictable for a pitcher his age. Jack Wilson probably suffered some from his preseason appendectomy, but the Pirates signed him to a two-year contract after the appendectomy took place, and the Pirates shouldn't have counted on him to hit the way he did in 2004 anyway. Wilson's final numbers were similar to his pre-2004 stats, and he had one of his two best months of the season in May, so it seems likely that the appendectomy was only really affecting him much in April. Mike Gonzalez was injured part of the season, but he was very effective when he did pitch, and he has a long history of injury issues. Only the injuries to Craig Wilson were both unexpected and particularly costly (and Wilson was also quite good when he played; he was hardly the "non-factor" Eagle says he was).
All teams have injuries; over the course of a season, most teams will also have injuries to key players. The injuries the Pirates faced were not unusual, particularly given the ages and injury histories of some of the players who got hurt.
Meanwhile, Zach Duke, Paul Maholm and Chris Duffy easily exceeded expectations, making up for a lot of the injury troubles. And while nearly everyone thought Jason Bay would be good going into 2005, it was hardly a given that he'd blossom into one of the best hitters in baseball. [EDIT: To his credit, Eagle does point out some of this.]
The Pirates won 67 games in 2005. They were, basically, a 67 win team, or close to it. While we all expect propaganda from Ed Eagle and MLB.com, Eagle is making a mistake a lot of fans make. The 2005 Pirates weren't ever likely to finish at .500 or better, and saying that injuries prevented them from breaking even overlooks the facts that they didn't even have terrible luck with injuries and that they had some good luck too.