When looking back at the year in boxing as a whole in 2019, it would be difficult to argue against the idea of Andy Ruiz Jr.'s stoppage of unified heavyweight champion Anthony Joshua in June being the unanimous choice for biggest upset and most shocking moment. But let's not forget the case that could be made for what Manny Pacquiao accomplished. 

At the tender age of 40 and in his 25th year as a professional fighter, Pacquiao (62-7-2) made an almost unthinkable case for fighter of the year by turning back the clock with a pair of high-profile victories on pay-per-view and making an emphatic return to the top of the rankings in boxing's deepest division. 

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Despite a full-time role as a senator in his native Philippines and fresh off just one appearance in 2018 when he stopped the ultra-faded Lucas Matthysse to snap a nine-year knockout drought and win a secondary WBA welterweight title, Pacquiao added yet another chapter to his legendary career. Even more impressive, he doesn't appear to be finished in his pursuit of the biggest and most dangerous names. 

Pacquiao began 2019 by pitching a near shutout of Adrien Broner in January, badly hurting him twice late in the fight. He came back six months later to floor unbeaten Keith Thurman en route to an exciting split-decision win to claim the full WBA title. 

The key for Pacquiao's resurgence seems to be both the absurd retention of his hand and foot speed and a rededication to his training, which seemed to be lacking in recent years (especially ahead of his 2017 upset title loss to Jeff Horn). The "PacMan" still packs enough power to keep opponents honest and his ability to confuse and harass by attacking from awkward angles hasn't gone away. 

So which opponents could end up in Pacquiao's plans for 2020? Some of that depends upon whether the new trend of rival networks joining forces to produce big fights (including the Feb. 22 Deontay Wilder-Tyson Fury PPV rematch with Fox and ESPN) continues to evolve. The specific details of Pacquiao's contract with Premier Boxing Champions (rumored to have either one or two fights remaining) also should play a role. 

If Pacquiao proved anything last year, it's that he can still draw as a brand after combining for the most PPV buys in 2019. Let's take a look at his six most intriguing options for the year to come. 

Errol Spence Jr. (26-0, 21 KOs)

The unified WBC and IBF welterweight champion recently made his first public appearance since a scary October car crash that saw him ejected from his vehicle and charged with DUI. The 29-year-old Spence not only said he expects to be back this spring, he wants to get right back at it against the biggest names, including Pacquiao and Danny Garcia, the latter of which he originally planned to fight in January. The southpaw Spence shut out Mikey Garcia last year before edging Shawn Porter in a fight-of-the-year contender. A fight against Pacquiao would not only be ultra competitive on paper, it would give PBC founder Al Haymon the best opportunity at expanding Spence's global brand. For Pacquiao, he would be entering a fight he can win. Spence has many questions to answer both mentally and physically. Porter also showed that educated pressure and foot speed are an opening for success against Spence as long as you have the chin to stand with him. If PBC believes Spence is ready so soon for such a big fight and writes a check large enough to make it worth it for Pacquiao, there's no reason why this couldn't be next.

Danny Garcia (35-2, 21 KOs) 

The former two-division champion has only lost in close and debated decisions against Thurman and Porter. With Spence still recovering from his accident, the 31-year-old Garcia will look to stay busy on Jan. 25 against brawler Ivan Redkach. If DSG wins, he has publicly stated his preference is a PPV date with Pacquiao in a fight that would potentially be big business given Garcia's history as a ticket seller. From a style standpoint, this is also a much more favorable matchup for Pacquiao than Spence considering Garcia's trouble with quick boxers who dart in and out with regularity (Porter, Lamont Peterson and Mauricio Herrera). The contrast in styles is also a marketable one as Garcia just might be the biggest puncher in the division from the standpoint of being able to end a fight with one shot. The chances of this fight happening in the first half of 2020 seem strong, especially if PBC uses it as a launchpad for Pacquiao to close the year in an even bigger fight, possibly against Spence. 

Shawn Porter (30-3-1, 17 KOs)

Although Porter lost his WBC title to Spence in a thrilling barnburner, the 32-year-old wrecking ball took home one heck of a moral victory by proving he's every bit as elite as anyone in the division. Porter has found the perfect balance between his default pressure style and the use of both feints and footwork to vary his attacks. The allure of a PPV bout against Pacquiao would be the guaranteed explosion of seeing two pressure fighters duel in the kind of track meet that has the term "high-speed chess" written all over it. Pacquiao has said repeatedly over the past year that he prefers opponents who bring the fight to him as its the easiest way he can please fans by creating an action fight. Pacquiao already proved his chin is still rock solid as he took Thurman's best shot and never backed down. The chances of a Porter fight likely comes down to whether Pacquiao prefers it over his other options.

Porter could be the perfect dance partner for Pacquiao in 2020. Getty Images

Terence Crawford (36-0, 27 KOs)

The fact that Top Rank founder and Hall of Fame promoter Bob Arum was unable to make this fight just two years ago when he had both welterweight stars under contract doesn't help the likelihood that we see it now when they are on opposite sides of the street. There have been some changes to both fighter's circumstances that could help, however. The reason why Pacquiao avoided a potential passing-of-the-torch fight against Crawford, the WBO champion, seemed to have more to do with money. Despite his pound-for-pound credentials, Crawford wasn't yet established as a giant draw outside of his native Omaha, Nebraska. Pacquiao also had tax issues that made fighting in the U.S. difficult (an issue that has been rumored to be rectified once Pacquiao joined forces with Haymon). Crawford is now a much bigger star thanks to the promotional vehicle of ESPN and the switch-hitter is also desperately out of big-name options that aren't under the PBC banner. Could the reality of the Wilder-Fury fight and the thawing of the spoiled relationship between Arum and Haymon lead to a Pacquiao-Crawford showdown this year? It's certainly not impossible. It's also not likely, however. Regardless of the exact amount of fights left on his PBC deal, Pacquiao is too valuable to Haymon as a brand for him not to try and "give the rub" to any number of PBC fighters he can match with him. 

Mikey Garcia (39-1, 30 KOs)

The former three-division champion may have come up empty in a one-sided loss to Spence in 2019 after moving up in weight, but the 32-year-old Garcia has huge plans at welterweight moving forward. Garcia recently signed a one-fight deal with future options to fight on DAZN under the banner of Eddie Hearn's Matchroom Sport. He will make his debut on Feb. 29 against former champion Jessie Vargas with the hope that a victory will propel him into the Pacquaio fight he has coveted publicly for years. How do we get there? With the specifics of Pacquiao's PBC deal having never been made explicitly public, there is still some debate as to whether he will be a free agent midway through 2020. If that's the case, DAZN has shown it has access to more money to lure a big name than any other network in the sport. Pairing Pacquiao's star with Garcia's talent and Mexican-American fanbase would give the upstart streaming app a must-see fight to close the year. In the end, this is a business and money talks. This fight is certainly in play. 

Floyd Mayweather (50-0, 27 KOs)

Considering their 2015 super fight produced a record 4.6 million PPV buys and reportedly netted Pacquiao close to $100 million, there's no question a rematch would be his biggest possible payday. The fact that Pacquiao has reclaimed status as a true elite and that he's fighting under the same adviser in Haymon who helped make Mayweather a household name certainly doesn't hurt either. There's too much money at stake to ever say with confidence that this fight couldn't happen or won't. The demand from casual and mainstream fans would instantly make it the biggest fight of 2020. That doesn't mean it's likely, however, even with Mayweather's constant rumbling about an in-ring return. The reason? Mayweather, who turns 43 in February, is too smart of a businessman and matchmaker. According to UFC president Dana White, who has teased a move into boxing for more than a year, he and Mayweather made a handshake deal courtside at a recent NBA game to join forces for boxing match later this year. The duo teamed up in 2017 to make a killing from Mayweather's one-off against MMA star Conor McGregor, which makes it much more likely Mayweather would explore a similar level of matchmaking than risk his unbeaten record against such a dangerous version of Pacquiao. Let's not forget, Mayweather came back more than a year ago to knock out a 20-year-old kickboxing phenom who was more than 20 pounds lighter than him in an exhibition bout in Japan for big money. Easy money is hard for him to pass up.