Dallas Braden's latest DL trip

As postseason propositions go, the A's October hopes rest pretty heavily upon the availability of their best rotation starters. With a core four aged 27 or younger, the young guns of Oakland represent the team's best weapon in an AL West race, especially with the expectations that young equals "bound for bigger and better things." And in the age of hyper-awareness of pitch counts and carefully managed workloads, that's an expectation that may be more reasonable to harbor for young pitchers than it has been in decades.

Unfortunately, every well-laid plan has the problem of running up against the realities of asking people to make their living doing an unnatural act -- like throwing a baseball -- and how hard it can be to sustain a career doing it. The news that Dallas Braden is making another trip to the DL hardly represents a surprising development for the hero of 209: in the big-league portion of his career alone, Braden has already spent significant chunks of 2009 and 2010 on the DL.

However, the especially bad news is that this latest injury is the return of an old bit of bad news. Where 2009 was an unusual injury (an infection in his left foot that wound up causing nerve damage and cost him two months), and 2010 was his soreness and inflammation in his forearm and elbow (costing him a month), this latest injury is a stiff shoulder -- the same joint that Braden needed surgery on back in 2006.

How well can the A's get by without him? Last year's rotation relied fairly heavily on his contributions, as his 2.9 WAR rated third behind those of Trevor Cahill (4.2) and Gio Gonzalez (4.0). Even though WAR's a cumulative stat and not a rate metric, Braden's relative ranking isn't cheated by his absence last year. From among last year's front four in Oakland, here's where his contributions ranked:

As far as a few quick explanations, SNWP is Support-Neutral Winning Percentage, a metric which gives you an idea of what a team's expected winning percentage should be in the guy's starts, with .500 being the definition of mediocrity. Last year, Felix Hernandez and Roy Halladay gave their teams MLB-leading SNWP marks of .646, which is another way of saying that the non-Braden trio rated pretty high last year -- among pitchers with 100 or more innings, Cahill (10th), Gonzalez (19th) and Anderson (22nd) rated well up the leader board. Braden clocked in with a still creditable 41st overall, so on most teams, his departure might be seen as crippling. For the A's, he's fourth man in an excellent front four.

The other metric you may not be familiar with up there is SIERA, which sabermetricians Matt Swartz and Eric Seidman developed on Baseball Prospectus last year, finding that it does a little bit better than FIP or xFIP. What it's particularly handy for is giving you a broad-strokes indicator of which way a guy's ERA is subsequently likely to go -- which in the case of Braden in particular takes us a wee bit closer to mediocrity, not that teams can't win pennants with a fourth starter with an ERA around 4.50.

This isn't the same thing as saying that Braden won't be missed during his absence of an as-yet-to-be-determined length, because there's a lot of value to being able to pitch only a little bit better than average over the duration of baseball's six-month season. (Witness the bidding on starting pitchers every winter.) The problem should also be less one of replacing Braden for two or three turns in the rotation, especially if fifth starter Brandon McCarthy remains among the hot hands of spring and pitches like he was making up for lost time. Which McCarthy is, having once been rated among the top 50 prospects in baseball (by Baseball America, before 2005), before he was felled by a litany of injuries almost as long as he is tall at 6-foot-7.

There's a bigger problem beyond the concern for Braden created by his absence, though, or the hope that his replacement -- probably either Tyson Ross or Bobby Cramer -- does well. Ross is a good enough prospect that he'd rate well as most people's fifth man, while Cramer's a root-worthy underdog as a well-traveled veteran of the independent leagues as well as Mexico. Thanks to a couple of days off and the way the schedule unfolds, if Braden only misses the minimum the A's will only need a fifth starter once in that time. No, the real question with Braden's setback is whether or not this is the latest unhappy development for an A's team only too used to seeing players break down, including three of these core four starting pitchers last year, because both Cahill and Brett Anderson also spent time on the shelf last season. Maybe some of that was caution, but could this be a return of last year's problems?

The hope was that things might improve with yet another non-player staffing change in the trainer's room. After a lot of turnover on the training staff in the past few years, Nick Paparesta is in his first year as the team's latest head trainer, having come over from the well-regarded, award-winning Rays' operation. Paparesta's hiring was taken as a step in the right direction, but with Braden's latest breakdown, you can understand the broken-record element to this story as far as the A's are concerned.

At best, losing Braden to an injury can serve as a three-part reminder of sorts: that perhaps no amount of diagnostic acumen can prevent some players from breaking down, that an ability to maintain health is an underrated skill, and that it's a skill that, almost as a matter of professional hazard, few pitchers ever master.

The last thing the A's need now is another cause to question whether or not they're going to see another season handicapped by too much time lost to injuries. With Braden joining closer Andrew Bailey and key set-up reliever Michael Wuertz on the DL, you can wonder if the A's aren't dealing with a more basic problem -- that perhaps it wasn't the trainers, but the on-field talent itself that's the issue. If health is a skill, and it's one the A's turn out to lack, their chances of unseating Texas might take even bigger hits than Braden's latest setback in the long season to come.

Christina Kahrl helped found Baseball Prospectus in 1996, is a member of the BBWAA, and covers baseball for ESPN.com. You can follow her on Twitter here.