It’s August in Oakland, and that’s meant stretch drive excitement year after year since 1999, Billy Beane’s second season in the general manager’s chair. The Athletics’ run of success has been fueled by great finishes. Once the calendar flips over to August, Oakland’s stretch drives for the last eight years have involved winning at a .637 clip in the season’s final two months from their more stolid .549 pace beforehand over that same stretch.

But not this year, not with the A’s mired in third place, not when they’re a dozen games behind the Angels of Anaheim, five games under .500, and nine out of the wild card race. This year, the home of the “Moneyball” mindset has delivered, well, irrelevance.

For some of us on the analysis beat, it’s not a welcome development, but it should only end up generating even more controversy within the press’s interpretations of Beane’s principles of management in baseball. Those principles — ably captured by Michael Lewis in his bestseller, “Moneyball” — helped put the A’s into playoff races for the last seven years. Predictably, Lewis’ assertions of Beane’s genius via a market-minded methodology generated much reaction within the conservative baseball industry. It generated old-school carping for why the A’s couldn’t win postseason series (until they did), and how that might somehow invalidate the proposition that a baseball team can be managed like a commodities market: Find undervalued assets — players — and employ them to your advantage.

It is still remarkable the extent to which this sensible approach generates so much backlash, yet nevertheless reigns as the paradigm that has changed the behavior of general managers throughout the game — in the amateur draft, at the trading deadlines, or during the hot stove league every winter. There might be something generational as far as the wisdom of controlling costs instead of throwing ever-larger amounts of money at any problem. Consider the contrast between the Diamondbacks’ decision in both this year and last to retool by calling up prospects while still sustaining playoff bids to Philadelphia Phillies general manager Ed Wade’s ever-larger investments in mediocre veteran relievers that never propelled his club any further forward. These days, there shouldn’t be questioning the market-inspired wisdom of exploiting under- or unappreciated assets in the form of ballplayers with somewhat non-obvious skills.

So while a solid cadre of younger or adaptable front office staffers have internalized these ideas, you can still expect a bit of crowing as the A’s run at relevance in the standings comes to a crash this year. This is perhaps the lesson “Moneyball” didn’t impart. If everyone in the market acts in the same way, then being especially clever in finding worthwhile and cheap pickups doesn’t represent an advantage any more. It’s just the difference between everyone else and the Pittsburgh Pirates. Players whose skills might have previously been recognized by very few teams wind up commanding the benefits of a lot more competitive interest in their services. When all the actors in a market understand that on-base percentage is a valuable thing, a nomadic backup catcher with nifty on-base skills — someone like the Toronto Blue Jays’ Gregg Zaun — sees his annual compensation jump from being a million-dollar bargain to more than 3.5 times that amount.

The A’s dependence on a rotating cast of affordable, good players getting picked up when their market value has dipped has faltered because of the laws of supply and demand. Scaring up useful players from among journeymen andminorleagueveterans, whether a starting pitcher like Gil Heredia or a slugger like Matt Stairs — both Beane finds from the late 1990s — gets a lot more difficult when everyone knows to fish those waters. Getting brilliant throw-ins like Mark Ellis or Cory Lidle, or undervalued relievers like Jason Isringhausen or Billy Taylor, only becomes more difficult. Beane’s competition has learned to listen and look that much closely at what he’s asking for, and the very act of pursuing unrecognized players who might be able to contribute eliminates their anonymity.

That’s led to the A’s depending more on finding aging free agents who might be willing to settle for short-term deals, whether it was the one-year investments in Frank Thomas as the club’s designated hitter in 2006, or this year’s less-happy pickup of Mike Piazza. The A’s are reduced to taking a chance on an underpowered left fielder like Shannon Stewart, and lucky in getting a moderately useful season out of him.

Injuries have also played a part. What now seem like a pair of regrettable commitments made to third baseman Eric Chavez in 2004 (six years, $66 million, running through 2010) and center fielder Mark Kotsay in 2005 (all told, more than $29 million for four years, ending after 2008) were defensible if you saw both players as they were seen at the time — as premium defenders at important positions with excellent track records as hitters. Now both have seen their production and availability sapped by injuries, and much of whatever financial freedom of action Beane may have enjoyed has been soaked up by calculations that didn’t work out as well as anticipated.

Injuries have also ruined the franchise’s usual harvest in prospects. Shortstop Bobby Crosby and starting pitcher Rich Harden were both seen as homegrown stars of the future. Beyond Chavez, the A’s system had produced stars like shortstop Miguel Tejada, catcher Ramon Hernandez, and starting pitchers Tim Hudson, Mark Mulder, and Barry Zito. Those players still exist in this organization — rookies like outfielder Travis Buck and catcher Kurt Suzuki figure to be lineup regulars, and they’ll eventually be joined by first baseman Daric Barton. But as Crosby and Harden demonstrate, even the pearls you carefully build up and harvest can lose their luster.

What’s to be taken from this year’s drop off? That a more competitive environment of a league and a sport with an improved level of parity on the field makes it difficult to live down mistakes on the ledger book. That also makes for a more fragile bid for contention—much of the difference between this year’s collapse and last year’s division title is the difference between less-damaged versions of Chavez, Kotsay, and Crosby, and between a healthy Frank Thomas and a broken Mike Piazza. The smart money says that contending in the future isn’t going to get easier.

Ms. Kahrl is a writer for Baseball Prospectus. For more state-of-the-art commentary, visit baseballprospectus.com.