By Jake Donovan

The countdown to the end of Manny Pacquiao’s historic boxing career is officially underway.

More than 21 years after turning pro way back in 1995, the former eight-division champ will fight for what could be the final time in his Hall of Fame-bound career on April 9 at MGM Grand in Las Vegas. The event will feature a familiar foe, as the wildly popular southpaw from Philippines will face Timothy Bradley Jr. for a third time.

"The deal is in place," Hall of Fame promoter Bob Arum told BoxingScene.com. "Manny still has to announce it, which should come (soon)."

The bout will come two years – almost to the day – after their April ’14 rematch, in which Pacquiao claimed a unanimous decision win to regain his welterweight title. The feat avenged a highly questionable loss he suffered to Bradley in their June ’12 clash.

Each of the previous two affairs between them were staged at MGM Grand, which will now play host to Pacquiao’s 10th consecutive Las Vegas-based fight. The event will air on HBO Pay-Per-View, his eighth straight by the time he and Bradley square off in April and 26th career appearance between HBO and its PPV arm.

The fight will be Pacquiao’s first (and potentially last) ring appearance since losing a unanimous decision to Floyd Mayweather in their long-awaited – but ultimately disappointing – superfight this past May. The five-year delay in getting the sport’s two biggest stars and best boxers in the ring proved well worth the wait from a financial standpoint, establishing records at the live gate and Pay-Per-View sales that will likely never be broken.

Mayweather followed up the win with a final encore of his own, a 12-round shutout of Andre Berto before electing to call it a wrap on his own incredible career. The undefeated boxer went out on top, even if the event proved underwhelming.

Pacqauiao, meanwhile, was forced to sit on the sidelines for the remained of 2015. The most belted fighter in boxing history – winning lineal championships and major titles in a record eight weight divisions – reportedly suffered a shoulder injury prior to the Mayweather fight, which he reaggravated during the bout itself.

During his downtime, it was decided that one more fight was necessary before deciding to pursue a full-time career in politics. Already a congressman in the Philippine province of province of Sarangani, Pacquiao has officially entered the race for one of the 12 Senate seats under his independent political party, the aptly named People’s Champ Movement.

Whereas he was able to go back and forth between roles as a boxing superstar and Philippines congressman, manning a senatorial seat is a full-time job. As such, Pacquiao will leave behind the sport that made him richer and more popular beyond his wildest dreams.

Still, the event is being sold on the merits of the rivalry and Pacquiao’s star power, not so much a farewell tour.

“We won’t sell it as Manny’s final fight,” Arum told BoxingScene.com on Tuesday. “We won’t do that for the simple fact that – anything could happen. Sure, it could very well be his last ever fight. But should he turn around one day and say he wants to fight again, we will look like a bunch of hucksters in selling the fight that way.

“I don’t want anyone accusing us of trying to tug at the heartstrings and claim this is it for Manny. Say for example, if Floyd Mayweather decides he wants to have one more fight, he’ll have to explain why he’s coming back after claiming he was done after the (Andre) Berto fight. We’re not going to put Manny in that position.”

Regardless, it’s no guarantee that he comes out victorious on April 9.

In choosing Bradley (33-1-1, 13KOs), he lands a reborn two-time welterweight titlist who remains among the world’s best fighters, regardless of weight-class. The always-sculpted boxer is coming off of a 9th round knockout win over Brandon Rios in November, his first fight under new trainer Teddy Atlas following a messy split from longtime chief second Joel Diaz.

The addition of Atlas adds a new dimension to an old rivalry, even if news of the fight itself isn’t being overwhelmingly embraced nor is it immediately known if Bradley’s welterweight title will be at stake. The belt he reclaimed in June now carries an overdue mandatory title defense versus Sadam Ali, who for the moment doesn’t seem keen on having to once again step aside.

Talk has already surfaced of Ali possibly facing Jessie Vargas in a vacant welterweight title fight, which presented an early warning sign that Bradley was going to land the coveted assignment. The 32-year old from Palm Springs was one of three final candidates named to land the fight with Pacquiao. Also included on the short list was unbeaten two-division champ Terence Crawford. Pacquiao, Bradley and Crawford are all promoted by Top Rank.

In that regard, Amir Khan was always viewed as a longshot among the trio previously named as was a late entrant in Adrien Broner. The four-division title claimant was contacted by Pacquiao’s chief adviser, Michael Koncz prior to the winter holidays. No sooner was he mentioned as potential candidate was he immediately dismissed from the running.

“The idea that Broner can sell tickets and Pay-Per-View buys with his mouth and trash talking, quite frankly, is ludicrous,” Arum told BoxingScene.com of the brash boxer from Cincinnati, who along with Khan is advised by Al Haymon, with whom Top Rank is currently embroiled in a $100 million lawsuit.

Pacquiao and Khan were former training stablemates, as both trained for years under the tutelage of Hall of Fame cornerman Freddie Roach out of his Wild Card Gym in Hollywood.

Khan has since moved on, relocating his training headquarters to the Bay Area where he now seeks corner advice from Virgil Hunter. Pacquiao and Roach remain together, as boxing’s dynamic duo has been together since 2001.

Over that time, Pacquiao – at the time a former World flyweight champ – added titles in seven weight classes, beginning with his stateside breakthrough performance. Accepting assignment as a late sub, Pacquiao scored a stunning 6th round knockout of then-top rated super bantamweight champ Lehlo Ledwaba in Las Vegas to emerge as a fighter to watch.

The win came on the undercard of an HBO Pay-Per-View telecast headlined by Oscar de la Hoya. The two were six weight classes apart at the time as de la Hoya added the super welterweight title to his arsenal with a 12-round win over Javier Castillejo. They would meet more than seven years later, with Pacquiao forcing de la Hoya to quit on his stool after eight shockingly one-sided rounds in their Dec. ‘08 welterweight clash.

A title wasn’t stake in the fight, but the feat itself saw Pacquiao’s status advance from boxing star to worldwide superstar. He would go on to make history, collecting a fourth World (lineal) championship in his next fight – a 2nd round knockout of Ricky Hatton in May ‘09 – followed by a welterweight-title winning 12th round knockout of Miguel Cotto that following November.

The win over Cotto gave Pacquiao a title in a record-breaking seventh weight class, adding a super welterweight belt to his arsenal with a 12-round win over Antonio Margarito in their Nov. ’10 catchweight bout in Dallas, Texas.

Just eight fights have followed since then, all taking place in either Las Vegas or Macau, China, and against only six different opponents. Two of the eight were against another longtime rival in Juan Manuel Marquez, with their third and fourth fights taking place over that stretch. Pacquiao was held to a draw in their epic first fight in 2004 before scoring narrow wins in 2008 and again in 2011.

By the time of his fourth fight with Marquez, Pacquiao was an ex-champion as a result of the controversial loss to Bradley six months prior. After three debatable decisions featured in his rivalry with Marquez, a definitive ending was delivered in their final bout – with Pacquiao suffering a shocking one-punch 6th round knockout loss.

The setback was met with a delay, but also for the opportunity to help Hall of Fame promoter Bob Arum launch his boxing business in Macau. Pacquiao’s ring return came 11 months later at resort location, outpointing Rios in Nov. ’13. It was viewed a high-profile tune-up fight, enough to get him back in the win column and in line to reclaim his old title. He did just that in his win over Bradley in their second fight.

Despite their series knotted at one apiece, there was never much demand for a third fight. It can be argued that such demand still hasn’t materialized, although recent changes endured by both fighters – in and out of the ring – potentially change that viewpoint.

Whatever the case, the mystery is now solved in the particulars surrounding the 66th – and possibly final - fight of Pacquiao’s historic career.

“Whether it’s the final fight, or “just” his next fight, we are going to pull out all of the stops and treat it like a big event,” Arum informed BoxingScene.com. “We’re going to dress it up with all of the bells and whistles, put on a strong undercard and present it as the first truly big PPV event of 2016.

“If it’s his last fight, then Manny can then announce his retirement afterward. We’re not going to make that the focal point. It’s a terrific fight between two outstanding gentlemen who represent the sport – in and out of the ring – with class.”

Jake Donovan is the managing editor of BoxingScene.com. Twitter: @JakeNDaBox