There have been only a handful of welterweight title unification bouts in the long history of boxing, but it turns out that September is a popular month for the rare event.

The 11th welterweight title unifier in boxing history will be added to the record books on Saturday, September 28 when undefeated Errol “The Truth” Spence Jr. and “Showtime” Shawn Porter face off at Staples Center in Los Angeles. The highly anticipated showdown is aired on PBC on FOX Sports Pay-Per-View at 9 p.m. ET/6 p.m. PT and has all the makings of a fight of the year candidate.

Spence (25-0, 21 KOs) is the IBF World Champion at 147 pounds and a slick, powerful southpaw who has knocked out 84% of his opponents. Porter (30-2-1, 17 KOs) owns the WBC belt and has a well-deserved reputation as a pressure fighter who seeks to overwhelm his opponents with a style that could have been formed as a high school football star in Cleveland.

As we count down the days to Spence vs. Porter, here is a look at four 147-pound unification bouts over the last 40 years.

“SUGAR” RAY LEONARD VS. THOMAS “HITMAN” HEARNS

Date: September 16, 1981

Location: Caesars Palace Outdoor Arena, Las Vegas

Records: Leonard 30-1 (21 KOs), Hearns 32-0 (30 KOs)

Result: Leonard TKO 14

Summary: The early eighties were the golden era of the welterweight division, with future Hall of Famers such as Leonard, Hearns, Roberto Duran and Wilfred Benitez; the cream of the crop who fought each other multiple times. The best of the lot were Leonard, the WBC champ, and Hearns, the “Motor City Cobra,” who held the WBA title. In 1981, the WBA and WBC were the only sanctioning belts that counted. This fight, known as “The Showdown,” would decide the undisputed champion.

Early in what was arguably the greatest welterweight title fight of all time, the long and lean Hearns kept a shorter Leonard at bay with his stiff jabs. But Leonard, a great ring strategist, turned on the aggression in the middle rounds and went on the attack. That lasted a few rounds before Hearns adapted, stopped brawling, and started boxing. The fight began to turn at that point, prompting Leonard’s trainer, Angelo Dundee, to famously tell his fighter after the 12th round, “You’re blowing it now, son, you’re blowing it. … We need fire and you’re not firing. You’ve got to be quicker.”

Leonard heeded the warning and attacked Hearns, knocking him down in the 13th. In round 14, Leonard, his left eye badly swollen, unloaded on Hearns with a lightning-quick flurry, leaving the “Hitman” hanging on the ropes before referee Davey Pearl stepped in and waved it off.

“We were both in our prime, we had faced other opposition that was on our level,” Leonard recalled. “It was probably a 50-50 fight, but maybe because of Tommy’s power, like knocking out Pipino Cuevas, he just annihilated people. In my camp, some of them thought Tommy was going to demolish me. But I fought the best I ever had, and he brought out the best in me.

Postscript: The rematch didn’t happen until 1989, when they were fighting for two titles at super middleweight back at Caesars Palace. It ended in a draw but, in fact, Leonard had missed five of the eight years and fought only four times between Hearns fights, including his amazing middleweight title victory over Marvin Hagler in 1987, where he was coming off just one fight in five years.

FELIX “TITO” TRINIDAD VS. OSCAR DE LA HOYA

Date: September 18, 1999

Location: Mandalay Events Center, Las Vegas

Records: Trinidad 35-0 (30 KOs), De La Hoya 31-0 (26 KOs)

Result: Trinidad MD 12

Summary: Billed as one of the great welterweight matchups in history, both fighters came into the “Fight of the Millennium” with unblemished records, and in the absolute prime of their careers.

The super fight that brought the curtain down on the 20th century also boasted the added grudge factor of Mexico (De La Hoya) versus Puerto Rico, the birthplace of Trinidad.

De La Hoya came out aggressively, outboxing Trinidad and seemingly building an early lead on the scorecards. By the ninth round, however, his pace had slowed considerably, and his corner felt he had built an insurmountable lead and advised him to stay away from Trinidad the rest of the way. That strategy backfired, of course, as Trinidad pressed the action late and rallied to win a majority decision. Judge Jerry Roth scored the bout 115-113 and Bob Logist had it 115-114, both for Trinidad, while Glen Hamada called the fight a draw, 114-114. With that, De La Hoya had lost for the first time, and in Las Vegas no less, where many thought it all but impossible for him to lose a decision.

The fight shattered the pay-per-view record for a non-heavyweight fight at that time with 1.4 million buys. De La Hoya earned nearly $25 million for his 36 minutes in the ring, while Trinidad was paid a little more than $10 million.

Postscript: Sadly, Trinidad-De La Hoya II never happened. Among the varied reasons is that the first fight was far from the slugfest most fans had expected. It turned out to be a major disappointment, mostly devoid of toe-to-toe action.

FLOYD “MONEY” MAYWEATHER VS. MANNY “PAC MAN” PACQUIAO

Date: May 2, 2015

Location: MGM Grand Garden Arena, Las Vegas

Records: Mayweather 47-0 (26 KOs), Pacquiao 57-5-2 (38 KOs)

Result: Mayweather UD12

Summary: The richest fight in boxing history was at least six years in the making, as the two sides could not come to terms on purse-split, drug-testing and location, not to mention the desire on both sides to let the fight marinate to increase interest in the long-anticipated matchup of two of the world’s top pound-for-pound fighters. And it worked, at least financially, setting records for live gate and PPV sales that may never be surpassed.

The fight itself was another story altogether and brought out the downside of the interminable wait. By fight night, Mayweather was 38 years old and Pacquiao 36, old for welterweights, but not so much for the combatants themselves, who seemed to defy age. Mayweather came in at 47-0 (26 KOs) and Pacquaio 57-5-2 (38 KOs), but neither had stopped an opponent for years.

Both fighters came out aggressively, but Mayweather’s defensive genius, jab and pinpoint counters, gave him each of the first three rounds on all three judges’ cards. Pacquiao went on the offensive in the fourth, finally landing some punches. By the late rounds Pacquiao, clearly frustrated by his inability to score on the still quick Mayweather, stayed on the offensive but was unable to land many meaningful punches.

Mayweather was in control through much of the second half of the fight, and won by unanimous decision, 118–110, 116–112, 116–112. He landed 67 more punches, according to CompuBox, than Pacquiao, one of the sport’s highest-volume punchers.

Postscript: Mayweather fought two sanctioned boxing matches after the richest fight ever, which racked up $410 million in revenue, including a record $72 million live gate, and sold 4.6 million pay-per-view buys, nearly two million more than the previous record. Mayweather, who earned more than $200 million for the Pacquiao fight, retired after defeating Andre Berto in September 2015 with a record of 49-0. He came out of retirement to stop MMA star Conor McGregor in 2017 in Las Vegas but retired again after earning an estimated $270 million.

To this day, Pacquiao believes he won that fight and is still pushing for a rematch, but so far Mayweather, now 42 and retired, has rebuffed the 40-year-old. Pacman has fought six times since and remains elite, handing Keith Thurman his first loss and taking his belt in July in Las Vegas.

KEITH “ONE TIME” THURMAN VS. DANNY “SWIFT” GARCIA

Date: March 4, 2017

Location: Barclays Center, Brooklyn

Records: Thurman 27-0 (22 KOs), Garcia 33-0 (19 KOs)

Result: Thurman SD 12

Summary: Keith “One Time” Thurman put his WBA welterweight belt on the line, while Danny “Swift” Garcia risked the WBC welterweight title he had won more than a year earlier from Robert Guerrero. Both Thurman, then 28, and Garcia, 29, were in their prime and unbeaten.

A Barclays record crowd looked on as Thurman came firing out of the gate with powerful combinations and pushed a frenetic pace. An overhand right followed by a series of wild bombs hurt Garcia in the waning moments of the opening frame, forcing him to hold on as the tremendous round ended. For five rounds, this was a classic matchup.

After that, “One Time” settled into a rhythm, circling away from Garcia’s best weapon, the left hook, and worked behind a crisp double jab. Thurman improved to 28-0 (22 KOs) using smooth footwork, lateral movement and timely punching. He eased up over the later rounds, though, allowing Garcia to work his way back into the bout. But it was too little, too late. The fight was scored 116-112 and 115-113 for Thurman, and 115-113 for Garcia.

Postscript: Thurman wouldn’t fight again for 22 months after undergoing surgery on his right elbow a few weeks after defeating Garcia. In January, Thurman edged Josesito Lopez by majority decision in his comeback fight. Thurman met his future wife during his hiatus, then met his match against Pacquiao in July, losing for the first time in his career by a narrow split decision. Garcia returned to Barclays a year ago to fight Porter for the WBC belt he had lost to Thurman, who had vacated the belt after his surgery. Garcia lost a unanimous decision to the fighter who will face Spence Jr. on Sept. 28. Whether Thurman and Garcia ever rematch remains to be seen.

The next welterweight unification promises fireworks. Here’s how “Sugar” Ray sees it: “I’ve watched Spence for years. He’s always improving, always in shape. I’ve watched Shawn, too. His fights are very exciting. But Errol is like a teacher in the ring. He has a lot of tools and he’s very poised. I like Errol in this fight, no question.”

Article courtesy of PBC