Gennady Golovkin vs. Kell Brook: Biggest Storylines Surrounding the Undercard

While Gennady Golovkin and Kell Brook headline the show at the O2 Arena in London on Saturday, there are plenty of other interesting stories set to play out on the undercard.

Brook steps up two divisions to challenge GGG for his WBC and IBF middleweight titles in the English capital, a battle between two unbeaten fighters that deserves pay-per-view status.

However, there are also two other world-title fights on the bill.

The chief support act is a long-overdue rematch between English bantamweights Lee Haskins and Stuart Hall.

Meanwhile, at flyweight, Charlie Edwards looks to prove he's ready to step up to the top table when he challenges IBF champion John Riel Casimero.

Here, Bleacher Report examines some of the major talking points away from the main event.

Back in the Big Time: Kid Galahad Gets the Chance to Impress

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Kid Galahad (left) has already fought once since having his ban shortened.

While his gym-mate Kell Brook shares top billing, Kid Galahad gets the chance to continue his comeback.

You wouldn't normally expect to find an unbeaten former British and Commonwealth champion buried down the bottom of a bill, but Galahad will welcome the opportunity to blow away the cobwebs.

The super bantamweight is back in action after having his two-year doping ban reduced by six months by United Kingdom Anti-Doping.

Galahad—who insisted his innocence after the positive test, stating it was down to a spiked protein drink—made his ring return earlier in the year. He stopped Simas Volosinas in April on a show in Wigan, England.

However, now he has the opportunity to appear on the big stage again. For a fighter with a desire to entertain, it is the perfect setting to remind a wider audience of his talent.

His opponent is Emiliano Salvini, an experienced Italian who has fought just the 329 rounds in his career.

Galahad told Sky Sports News HQ: "Salvini is very tricky and he has never been knocked out, although he has been stopped a few times. He can give you nightmares in the ring as he is very hard to hit."

The Rematch: Lee Haskins and Stuart Hall Settle an Old Score

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Lee Haskins will be hoping history is repeated in the rematch with Stuart Hall.

Lee Haskins and Stuart Hall is a wonderful appetiser before the main course.

The two English bantamweights will do battle for a second time in their careers, Haskins having won the first meeting back in 2012.

On that occasion, the vacant European title was on the menu. This time, however, Haskins brings the IBF belt to the table.

Hall—a former IBF champion—battled to a points victory over Rodrigo Guerrero in April to set up the opportunity to fight for a title he used to have in his possession.

However, at the age of 36, he recognises a defeat on Saturday could leave him with nowhere left to turn.

Stuey told Adam Steel of the Evening Gazette: "It’s a last roll of the dice for me, I’m climbing back up to the top of the snakes and ladders and if I hit the snake there is no coming back."

As for Haskins, the Bristol boxer became a world champion without throwing a punch following Randy Caballero's failure to make weight for their fight last year.

He plans to hand Hall a history lesson at the weekend, as he told Andy Stockhausen of the Bristol Post: "He's always boxed the same way. He walks forward, his feet are slow and he's there to be hit. My footwork and hand speed will be too good for him, just like they were last time."

The prize on offer adds a little extra spice to a rivalry that has been simmering away for years.

Brothers in Arms: The Smiths Stay Busy Ahead of Bigger Fights

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Paul Smith joins younger brother Callum in action at the O2 Arena.

Callum and Paul Smith may be at the opposite ends of their careers, but the brothers find themselves in a similar situation right now.

The siblings are both in action at the O2 as they wait for a world-title shot.

Callum is the mandatory challenger for the WBC super middleweight title. Badou Jack is the current champion, but his next outing looks certain to be a unification clash with IBF holder James DeGale.

Rather than sit back and simply wait for his opportunity, Mundo has opted to stay busy. He will defend his WBC Silver belt against Hungarian Norbert Nemesapati (21-3, 16 KOs). The bout is scheduled to go 12 rounds—it will be a major surprise if it even makes it beyond halfway.

As for Paul, the oldest of the four Smith brothers, he is targeting a different title in the same division.

Promoter Eddie Hearn said in an official Matchroom press release how Smigga has "one eye on the winner of the rematch between Giovanni De Carolis and Tyron Zeuge winner for the WBA strap."

In the meantime, Smith will box in a six-rounder in London before also appearing at the Echo Arena in his home city of Liverpool, England, in October, according to BoxRec.

While Paul sticks around in the hope of making it third time lucky—he lost twice to former WBO champion Arthur Abraham—little brother Callum keeps ticking over while he waits for a date.

Stepping Up: Can Charlie Edwards Make the Leap to World Level?

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Charlie Edwards has the chance to become a world champion in just his ninth pro fight.

For a flyweight who stands at 5'6" tall, Charlie Edwards sure has taken on a big challenge.

After just eight fights and with only 51 rounds under his belt, the 23-year-old has jumped at the chance to fight for the IBF title.

He goes up against holder John Riel Casimero, a far more experienced boxer who dethroned Amnat Ruenroeng in May by knocking the former champion out.

Edwards told Matchroom Boxing: "I’d be lying if I didn’t say that it’s come sooner than I expected, but I am going to grab this opportunity with both hands."

It is a huge leap of faith by the Englishman—he only won his national title less than a year ago.

However, if Edwards doesn't plan on hanging around for too long in the flyweight division, this is an opportunity simply too good to turn down.

While he is a two-weight world champion, Casimero has lost three times. Ruenroeng outpointed him in their first meeting, then lost the rematch having already made clear his plans to compete at the Rio Olympics.

In an interview with John Dennen of Boxing News, Edwards insisted he has a "great chin." He may need it on the night, but his engine will demand Casimero has to work hard to retain his crown.