I read a good article this Friday about the different philosophies of constructing a baseball team - October, Without All the Muscle. There was also a chart of "impact players", i.e. the players who have more of an impact on how many points their teams score. They claim that Youkilis is more valuable than Pedroia, at least in a series against the Angels.
I'll let you read it if you're interested instead of summarizing it myself, but one of the takeaway points is that teams like the Brewers and White Sox seemingly depend on fewer players to be successful than teams like the Rays and Angels, whose run production would not suffer as much if they were to lose a couple of key players. The Red Sox fall somewhere in the middle.
What do I take away from it? It seems like a lineup filled with only good players might be far more consistent and effective than one that is average except for 2-3 all-stars. It might not be so surprising that certain mid-market teams who simply can't afford free agent all-stars but are crafty enough to make thoroughly "pretty good" lineups are able to compete year after year.
Maybe this is obvious to people outside of Yankee-land.