“What begins as a failure of imagination ends as a market inefficiency.”

These words from the seminal sports book of a generation, Michael Lewis’ “Moneyball,” best describe what transformed Oakland A’s front-office guru Billy Beane into a cult icon and nerd hero. Here was someone bringing a true analytic style to baseball — leading one of the MLB’s most cash-strapped franchises to consistent success. Beane exploited the market for years by focusing on oft-overlooked statistics and by re-examining players with unusual physical profiles.

But almost 15 years after “Moneyball” was published, there’s a question A’s fans and even Beane himself must be asking.

What happens when the market adjusts?

The A’s made the playoffs five times from 2000 to 2006, winning 11 playoff games and posting a robust .586 winning percentage in the regular season over that span. Even though they never made a World Series, those are incredible results for a small market team.

But since? Over the last nine years, a .498 record with two postseason appearances — three if you count making a single-elimination wild card game and losing — without winning a playoff series. Those may be passable numbers for a small market team, but it’s pretty hard to fathom any other general manager keeping his job for a decade with this lack of tangible success. The reason for keeping him around this long has to be the belief among ownership that Beane’s genius as a thinker is sure to win out eventually. But that may just be wishful thinking.

Innovating something fantastic shouldn’t mean job security for life; front-office jobs don’t come with tenure. If other people can understand your innovation and apply it even better than you do, it’s time to take your place in the shadows of the game. Tex Winter is often considered for the legendary triangle offense that won Michael Jordan and Kobe Bryant 11 combined championships. But he failed as a head coach in the higher ranks of college ball and the NBA, eventually finding success as an assistant to the man who learned to implement his concept perfectly: Phil Jackson.

Buddy Ryan was an incredible defensive thinker in football, devising the fabled 46 defense that boosted the 1985 Bears to their notorious level in his time as the team’s defensive coordinator. For his achievements as a genius defensive inventor, he was given head-coaching positions with the Eagles and the Cardinals. He had some success in the regular season, but none in the playoffs — and was sent on his way quickly from both jobs. Once his defensive scheme was understood, others became better suited to execute it.

Beane truly was the only top executive operating in this analytic mode at the time of “Moneyball,” and the results speak to the success of his insights. But nearly two decades removed from Beane taking the job, baseball’s front offices are littered with former Wall Street employees and statistics majors who learned everything from a mythical book in which Beane perhaps revealed what was just a little too much of his scheme to the author. Baseball owes Beane a huge favor for ushering in the analytic age, but the A’s shouldn’t be the ones paying that favor by keeping him around past his expiration date.