I sometimes spend my free time looking at the backend of other team's rosters (c'mon people, the jokes write themselves).
I do it because I'm obsessed with baseball, but I think there's something to learn there, too. One point is that most rosters are filled out with deadwood and hope. Take, for instance, your World Champion Red Sox, who gave nearly 600 PAs to a combination of players who individually produced less than 1 WAR, and combined for only +0.1 WAR (hooray for David Ross' 0.9) (not counting Will Middlebrooks' obviously disappointing 0.3 WAR in 374 PAs).
We're talking about a full time player worth of trips to the plate where the best team in baseball got replacement level performance, which is, by definition, below league-average. And that's the best the team could do?
The Tigers only got 0.8 WAR from the players outside their top nine hitters. The Rangers got -0.1 after their top nine, the Indians exactly 0.0, the Rays 1.4 (hello Sean Rodriguez's 1.1 in 222 PA!), the A's 0.7 (how did Grant Green produce -0.6 WAR in only 5 games?).
Of course, one of the Yankees' problems last season was that their backups became their regulars. And, of course, the defensive metrics are so hard on certain players that you might suspect bias in the numbers. Eduardo Nunez's -18 defensive mark in 90 games is a big part of his team-low -1.4 WAR; Vernon Wells posted -6.1 runs as part of a -0.8 WAR; Derek Jeter was only -3.9 defensively in his -0.6 campaign.
Which is why I shrug a little when the Yankees stockpile outfielders or announce that Eduardo Nunez is The Alex Rodriguez Backup Plan. Anyone who can look at the 40-man roster can see that, right now, Nunez is the backup plan. And anyone who can look at the dearth of alternatives understands how fungible bench players are.
Even more so than assembling a bullpen, if you catch lightning in a bottle, great, but it's not your bench players who will win or lose the season. It's your starting nine. If you can stay healthy, you'll put seven or eight of your everyday players on the field each night.
Should Brian Cashman invest his resources and trade for a league-average third baseman or second baseman? It might make you feel better to know who's going out there every night, but does it actually guarantee to improve the team? Let Brendan Ryan and Kelly Johnson and the withered husk of Brian Roberts fight for playing time. Play the hot hand.