Which undefeated boxer has the best shot at finishing career unbeaten?

Sugar Ray Robinson. Henry Armstrong. Muhammad Ali. Joe Louis. Jack Dempsey. Sugar Ray Leonard. Marvelous Marvin Hagler. Mike Tyson. Many of the greatest fighters in boxing history were unable to accomplish the feat.

Retiring as a world champion with a perfect record – no losses and no draws – is one of the most difficult things for a boxer to do.

Robinson is widely regarded as the greatest boxer who ever lived. This story only considers professional records, but it’s not well known that Robinson was 84-0 as an amateur. He then won his first 40 fights as a pro before losing to the great Jake LaMotta.

Robinson followed his loss by winning 88 and drawing two of his next 90 bouts, to boost his professional record to an astounding 128-1-2, with 84 knockouts. Add in his 84-0 as an amateur and Robinson was 212-1-2 in the first 215 bouts he competed in.

But for this list, that doesn’t qualify. There are many who currently sport perfect records, so Yahoo Sports took several of the top active boxers who haven’t lost or suffered a draw and analyzed their chances of finishing as a world champion with a perfect record.

I put the fighters into three categories: Likely, Possible and Unlikely. The fighters I rated likely are guys who are near the end of their careers and who don’t have more than one or two serious challenges ahead.

Possible are those who are in mid-to-late career and face just a handful of difficult opponents.

And unlikely are those who are early in their career who have plenty of serious challenges ahead.

Likely to finish perfect

Andre Ward, 33 years old, IBF-WBA-WBO light heavyweight champion, 31-0, 15 KOs – Ward is already talking retirement and told Yahoo Sports recently if he fights again, it would only be against Sergey Kovalev. Ward defeated Kovalev on Nov. 19 in Las Vegas and they face a rematch ahead. Kovalev could have won that first fight and can’t be ruled out of the second. Biggest threat to perfection: Kovalev. Iole’s odds of finishing perfect: 4-1.

Guillermo Rigondeaux, 36, WBA-WBO super bantamweight champion, 17-0, 11 KOs – Rigondeaux relies on outstanding defense, an uncanny sense of timing, terrific reflexes and great counter punches to win his fights. The reflexes may decline as he ages, but the timing will stay with him. Despite his record and his two Olympic gold medals, not a lot of opponents are eager to face him because he doesn’t have much of a name any more and doesn’t fight a crowd-pleasing style. Top Rank’s Vasyl Lomachenko has moved up to super featherweight, but he might be convinced to drop back to featherweight for a fight against a fellow Olympic double-gold medalist. Biggest threat to perfection: Vasyl Lomachenko. Iole’s odds of finishing perfect: 4-1.

Roman “Chocolatito” Gonzalez, 29, WBC super flyweight champion, 46-0, 38 KOs – Gonzalez is still in his prime and is one of the best, if not the best, pound-for-pound boxers in the world. He’s an exciting offensive fighter who has good defensive skills. He’s moved up in weight, and that will put him at risk. How much longer he’ll fight is the question. He’s pretty much set financially now and it’s probably a good bet he’ll step aside after 50 fights. Biggest threat to perfection: Juan Francisco Estrada and Naoya Inoue. Iole’s odds of finishing perfect: 6-1.

Possible to finish perfect

Wanheng Menayothin, 31, WBC minimumweight champion, 45-0, 17 KOs: The lightest weight fighters face the biggest physical declines as they age, as sheer size and declining reflexes tend to take over. Menayothin, who is widely regarded as the best strawweight, still hasn’t shown a huge decline. Biggest threat to perfection: Thammanoon Niyomtrong. Iole’s odds of finishing perfect: 12-1.

Terence Crawford, 29, WBC-WBO super lightweight champion, 30-0, 21 KOs: Crawford is one of the most complete fighters in the world, as gifted defensively as he is offensively. He’s relatively young and that works against him, as does a series of potential quality opponents. Biggest threat to perfection: Danny Garcia. Iole’s odds of finishing perfect: 15-1.

Luis Ortiz, 37, former WBA heavyweight champion, 27-0, 23 KOs: Ortiz’s age is a likelihood that he’ll remain on this list. He will be 38 by the end of the month and he’s not the most active guy. There aren’t a lot of threats and those that are there are unlikely opponents. There are a lot of good heavyweights active now, like Anthony Joshua, Joe Parker and Deontay Wilder, but they don’t seem likely to compete with Ortiz. Biggest threat to perfection: Deontay Wilder. Iole’s odds of finishing perfect: 15-1.

Gennady Golovkin, 34, IBF-WBC middleweight champion, 36-0, 33 KOs: Golovkin is in magnificent condition for a 34-year-old, and loves boxing, so a quick retirement doesn’t seem like a option. But he’s going to be looking for big fights, and in 2018, if he’s still undefeated, will likely have to move up to do it. That’s where the biggest risk is, but not the only one. He’s facing Daniel Jacobs, who has only lost once, on March 18, with the prospect of a bout against Canelo Alvarez later this year. Biggest threat to perfection: Alvarez. Iole’s odds of finishing perfect: 15-1.

Unlikely to finish perfect

Keith Thurman, 28, WBA-WBC welterweight champion, 28-0, 22 KOs: There are a lot of big fights for Thurman in and around his weight class, and given his relative youth, he’s going to have to turn into an all-time great to remain perfect. He’s a strong combination of boxing and punching, but as he showed Saturday in his victory over Danny Garcia, he isn’t without fault. Biggest threat to perfection: Errol Spence Jr. Iole’s odds of finishing perfect: 20-1.

Naoya Inoue, 23, WBO super flyweight champion, 12-0, 10 KOs: Inoue is one of the best boxers nobody in the U.S. knows about, largely because he fights in a weight class that is largely ignored in the U.S. But if he ever attracted the attention of a U.S. television network, he’d become hugely popular in a hurry. Biggest threat to perfection: Roman Gonzalez. Iole’s odds of finishing perfect: 22-1.

Deontay Wilder, 31, WBC heavyweight champion, 38-0, 37 KOs: Wilder hasn’t faced great opposition more than eight years into his career, but there are a number of heavyweights he could fight who have the ability to defeat him. But Wilder has fast hands and punches exceptionally hard, two traits that overcome a lot of sins. Biggest threat to perfection: Anthony Joshua. Iole’s odds of finishing perfect: 25-1.

Oscar Valdez, 26, WBO featherweight champion, 21-0, 19 KOs: Valdez is one of the young, exciting fighters in the world and is clearly on the rise. But he’s got a decade or more left in his career and many significant challenges. Biggest threat to perfection: Vasyl Lomachenko. Iole’s odds of finishing perfect: 30-1.

Oleksandr Gvozdyk, 29, light heavyweight contender, 12-0, 10 KOs: A bronze medalist in the 2012 Olympic Games, Gvozdyk is a talented big man who is athletic, powerful, can box and hits hard with both hands. Biggest threat to perfection: Moving up in weight. Iole’s odds of finishing perfect: 30-1.

Errol Spence Jr., 27, welterweight contender, 21-0, 18 KOs: Spence was compared to Sugar Ray Leonard when he turned pro, and while it’s obvious why, he’s been moved slowly. He’s going to challenge Kell Brook for the IBF belt in May. Biggest threat to perfection: Keith Thurman. Iole’s odds of finishing perfect: 30-1.

Anthony Joshua, 27, IBF-WBA heavyweight champion, 18-0, 18 KOs: Joshua has been perfect as a pro, but he’s not without his faults. He can be hit and he hasn’t faced much opposition. He’s also occasionally stiff and doesn’t move well at the waist. But like Wilder, he can punch. Biggest threat to perfection: Wladimir Klitschko. Iole’s odds of finishing perfect: 32-1.

Gilberto Ramirez, 25, WBO super middleweight champion, 34-0, 24 KOs: Ramirez is the rising star in the loaded super middleweight division, and he could face challenges from not only within the 168-pound class, but from fighters moving up as well as guys now at light heavyweight. He’s a good, not great puncher and a solid, not complete, boxer. Biggest threat to perfection: Gennady Golovkin. Iole’s odds of finishing perfect: 40-1.