Gennady Golovkin is no longer the unified middleweight champion of the world. It sounds a bit funny and unusual to even type that out, given that he had dominated the division for several years.

On the night of Sept. 15 at the T-Mobile Arena in Las Vegas, he lost his belts in a razor-thin split decision to Canelo Alvarez in their rematch.

Punch stats for Canelo-GGG II Punches Alvarez Golovkin Landed 202 234 Thrown 622 879 Percent 33% 27% -- Courtesy of CompuBox

Golovkin is now belt-less and the cloak of invincibility is no longer draped upon him as it once was. While still a formidable fighter, he is no longer thought of as the fearsome force he once was, which is natural given that he is now 36 years old and coming off a long and storied amateur career that spanned 350 bouts (where he compiled a mark of 345-5 and captured a silver medal in the 2004 Olympics in Athens, Greece).

By 2019 he will be entering his 13th year as a professional prizefighter and he now has 40 bouts under his belt (38-1-1, 34 KOs). There is the sense that we have seen the best of GGG as he enters the twilight of his career.

Right now, the future is a bit uncertain for Golovkin. Currently, he and his promoter, Tom Loeffler, are sifting through various offers from networks and platforms that would like his services. Golovkin remains one of the most marketable fighters in the sport and where he lands will determine his most viable and realistic options. Which is the case for most boxers nowadays -- who you're associated with will determine what options you have in terms of potential opponents.

Since coming over to the United States in 2012, Golovkin has been under the HBO Sports banner, but the network recently announced it will be out of the boxing business at the end of this year. Regardless of his network affiliation, Loeffler was still able to reach across the aisle when it came to finding dance partners for his client. Whether it was cutting a deal to face Kell Brook in the UK with Eddie Hearn or Danniel Jacobs (when Jacobs was with Premier Boxing Champions), you would hope this trend would be allowed to continue in the future, regardless of where he lands.

With that said, what are the five opponents Golovkin should be facing in what will most likely be the final chapter of his boxing career? Well, here's a list that doesn't take into account the usual boxing politics or alliances that too often hinder match-ups from coming to fruition. Just five fights that would be entertaining and add to Golovkin's résumé.

1. Canelo Alvarez

Canelo Alvarez, right, defeated Genandy Golovkin in a rematch in September to become the unified middleweight world champion. Al Bello/Getty Images

Not only is Alvarez (50-1-1, 34 KOs), the Mexican superstar, the WBC and WBA belt-holder at 160 but he's the recognized middleweight champion of the world after his victory over Golovkin. Canelo has always been a box-office star with his matinee idol looks and strong backing from his Mexican constituents, but to his credit he has also developed into one of the most complete all-around fighters in the sport and is peaking as a boxer at 28 years old.

Currently, Alvarez is scheduled to fight again on Dec. 15 at the Madison Square Garden in New York against WBA "regular" super middleweight titlist Rocky Fielding. Most likely, Alvarez will return to 160 to defend his titles on the DAZN streaming service, where he inked a lucrative 11-fight, $365 million deal.

While most observers believed Golovkin clearly won their first encounter in 2017, opinion was split on their second match-up, which unlike most rematches surpassed the action and the drama of the original. You get the sense that Round 25 would only pick up from where they left off.

And keep this in mind, short of a Anthony Joshua-Deontay Wilder showdown, there is no other fight that will do as much business as Canelo-GGG III.

2. Jermall Charlo

WBC interim middleweight champion Jermall Charlo is one of the best opponents Gennady Golovkin could face in the near future. Photo provided by Andrew Hemingway/Showtime

The volatile puncher from Houston, Texas, is one of the most explosive punchers in all the sport and currently holds the WBC interim middleweight belt -- meaning that in due time he will eventually be the mandatory for Alvarez. While the sanctioning body "ordered" a Charlo-Golovkin fight, those really are more suggestions than mandates.

Charlo (27-0, 21 KOs), who faces Willie Monroe Jr. at the Barclay Center in Brooklyn on Dec. 22 on Fox, is in his physical prime at 28 years old and he certainly doesn't lack for confidence. The former junior middleweight titlist has created momentum with a series of eye-opening KOs, but the reality is that his middleweight run consists of a hobbled Jorge Sebastian Heiland (TKO4) and Hugo Centeno (KO2). But he does pass the "eye test." He's young, strong, athletic and powerful.

How would Golovkin deal with all this at his age? And how would Charlo deal with Golovkin's educated jab and power?

3. Callum Smith

Callum Smith defeated George Groves to win the World Boxing Super Series super middleweight final in October. Photo by STR/AFP/Getty Images

For years, Smith was known as a prospect, but he announced his arrival to the world class by stopping George Groves in emphatic fashion on Sept. 28 in Jeddah, Saudi Arabia. Not only did he take the WBA super middleweight crown by stopping Groves in seven rounds, but he won the Muhammad Ali Trophy as the winner of the World Boxing Super Series super middleweight tournament.

Smith (25-0, 18 KOs), who comes from a fighting family, makes a strong argument as the best 168-pounder on the planet. And there has already been some cursory discussions of this match-up between Eddie Hearn (who's company represents the native of Liverpool) and Loeffler.

Like the aforementioned Alvarez and Charlo, Smith is 28 and looks to be a fighter on the upswing. You figure that he will become only more emboldened after defeating Groves in the fashion he did. For years, Golovkin never really entertained the thought of moving up to 168, preferring to pursue his goal of fully unifying the middleweight belts and setting the record for the most successful title defenses at middleweight. At this stage, it looks like neither destiny will be fulfilled.

In Smith, Golovkin would be facing a long, lean boxer-puncher that has several inches on him as Smith is listed at 6-foot-3 and Golovkin at just a shade under 5-foot-11.

4. Jarrett Hurd

Jarrett Hurd, left, punched his way to a split decision victory over Erislandy Lara in April to unify two junior middleweight titles. Sam Wasson/Getty Images

"Swift" is currently the WBA/IBF junior middleweight champion and many wonder how -- and for just how long -- the native of Maryland can continue to squeeze into 154 pounds. One day he will be a middleweight but for the time being he will return to the ring on Dec. 1 on the Deontay Wilder-Tyson Fury undercard at Staples Center in Los Angeles to face little known Jason Welborn.

Despite his long, lean build, Hurd, 28, is a physical grinder who likes to work inside the pocket and relies on an active pace. You might be able to keep up with his punch output for a few rounds and perhaps even outbox him, but over the long haul he will swarm you with a torrent of leather that comes from all directions. Once the thundering Hurd (22-0, 15 KOs) gets going, it's nearly impossible to stave him off. Also possessing a stout chin, he's more than willing to take a few to give a half-dozen.

Golovkin would find Hurd a relatively easy target with his jab, but would he be able to hold off his constant pressure of 36 minutes?

5. Jaime Munguia

Junior middleweight world titleholder Jaime Munguia had a chance to face Gennady Golovkin in May, but he was denied by the Nevada State Athletic Commission. Photo by Tom Hogan/HoganPhotos/Golden Boy Promotions

If there is a breakout fighter of 2018, it has to be this hard-hitting young Mexican who burst onto the scene back in May by bludgeoning Sadam Ali over four rounds to win the WBO junior middleweight crown. Since then, he has won a 12-round decision over Liam Smith in July and then pounded Brandon Cook into submission in three rounds on the Alvarez-Golovkin II undercard in September.

If there is someone poised to be the next Mexican star, it's this 22-year-old from Tijuana, who not only possesses the hell-bent-for-leather style that is favored by his countrymen but has a boyish personality that resonates across the broad spectrum of fan bases within the sport. He's the type of fighter who punches first and thinks later -- and does it with a smile.

Munguia (31-0, 26 KOs) nearly faced Golovkin this past May 5 as Alvarez was suspended for testing positive for Clenbuterol and Golovkin made the decision to fight on this date, with or without him. But the Nevada Athletic Commission, led by Bob Bennett, nixed Munguia as an opponent in their jurisdiction and Golovkin was forced to fight in California versus Vanes Martirosyan.

It turned out to be rather fortuitous for Munguia, who simply may not have been ready for such a daunting assignment at that stage. As it turned out, he was able to grab a belt and get major exposure on HBO and major pay-per-view cards in the subsequent months and become a known commodity in the business.

No matter who Munguia faces, he will be who he is: a guy who will hurl punches as hard as he can for as long as he can and will continue to keep coming forward, regardless. However, this pairing would truly be about "Mexican style."