Oct. 4, 2016, stands as a stark and obvious dividing line for the two halves of what will be known in Baltimore as the Buck Showalter era. On that day, at Toronto’s Rogers Centre, the Orioles’ third playoff appearance in five seasons came to a sudden, premature end in a 5-2, 11-inning loss to the Toronto Blue Jays in the American League wild-card game — a contest remembered not for a move Showalter made but one he didn’t: Zach Britton, the closer having the best season of any reliever in years, never appeared in the game.

Nothing much went right for the Orioles in the months and years that followed, bottoming out with this year’s 47-115 disaster, the worst season in franchise history.

On Wednesday, Showalter’s eight-plus-year tenure with the Orioles came to end when the team informed him it would not be bringing him back as its manager in 2019 — part of an organizational housecleaning that also reportedly claimed general manager Dan Duquette, the architect of the rosters that Showalter guided to playoff appearances in 2012, 2014 and 2016. Duquette, 60, joined the Orioles in November 2011 — nine years after his last GM gig, with the Boston Red Sox.

“The club will hire an executive from outside the organization to lead the Baseball Operation department,” the Orioles said in a press release. “Once in place, this individual will have the final determination on all baseball matters that he or she believes will make the Orioles successful on the field, entertaining to fans, and impactful in the community.”

The news of both firings was first reported by The Athletic. While the parting with Showalter was not a surprise — days earlier, he had seemingly resigned himself to it, pronouncing himself “at peace” with whatever happened to him — there was some expectation the team would offer him another position in the organization, a move that apparently will not happen.

There had also been speculation within the industry that Duquette might survive as GM, and the Orioles had allowed him to preside over a large-scale sell-off of star players at the July 31 trade deadline, a wave of departures that included Britton, Manny Machado, Jonathan Schoop and Kevin Gausman.

Showalter, 62, was known as a shrewd strategist with an impeccable attention to detail when the Orioles hired him in July 2010. He also had a track record of turning losing franchises into winners — something he succeeded in doing again in Baltimore. The Orioles made a small leap in 2011, Showalter’s first full season in the dugout, then a huge one in 2012, winning 93 games and advancing to Game 5 of the Division Series before losing to the New York Yankees.

That launched a sustained era of success unseen at Camden Yards since the mid- to late 1990s, with the Orioles winning their first division title in 17 years in 2014, this time bowing out in the AL Championship Series, and earning a wild card in 2016. The fateful decision to hold Britton back for a potential save in extra innings of that 2016 wild-card game — a save opportunity that, of course, never came — hung over Showalter and the franchise ever since.

Showalter, the 2014 manager of the year, was close to Orioles owner Peter Angelos — for whom he lasted longer than any other manager in the latter’s tenure as owner. But as Angelos’s health deteriorated in recent months and the day-to-day operations of the team shifted to sons Louis and John, Showalter’s lame-duck contract status, as well as the Orioles’ horrendous 2018 season, made him an obvious target for an organization in need of radical change.

The team’s massive sell-off this summer, with higher-priced veterans dealt for younger players and prospects, indicated the start of what could be a lengthy and painful rebuild. Center fielder Adam Jones was close to being traded as well but used his veto power as a veteran player to shoot down a proposed deal to the Philadelphia Phillies.

While the team’s ownership situation remains in flux, with no clear sign of an organizational hierarchy or philosophy from the Angelos sons — or even a strongly declared intention to remain as its owners — the team must now replace the entire top tier of its management structure. A critical question will be where Brady Anderson — a former Orioles slugger, longtime Angelos confidant and the vice president of baseball operations — fits into the picture.

Wherever the Orioles go from here — and given their depths in 2018, the rebuild they have begun and the rarefied company they keep in the AL East, things are unlikely to get much better anytime soon — it will no longer be with Showalter in their dugout or Duquette in the front office.