By Jake Donovan

Floyd Mayweather enters what he firmly insists is the final fight of his incredible career, as the undefeated World welterweight champion meets Andre Berto in a scheduled 12-round bout Saturday evening at MGM Grand in Las Vegas, Nevada. 

Both fighters easily made weight for the Showtime Pay-Per-View headliner. Mayweather came in at an always-ready 146 lbs., while Berto was a ripped and lean 145 lbs. 

Saturday's show pales in comparison to Mayweather's last ring appearance—but then, any event would. The best fighter in the world further established himself as the highest-grossing athlete in boxing history following his 12-round win over Manny Pacquiao in their historic May 2 meeting in this very venue.

The event destroyed all monetary records, with Mayweather clearing well north of $220 million (some reports claiming as much as $250 million). Despite the gigantic cash grab, Mayweather insisted in finishing out his six-fight deal with Showtime, which leads us to this weekend in Las Vegas. 

Mayweather and his handlers have not budged from the claim of this being the last ever-fight of his 19-year career that is undoubtedly Canastota-bound in his first year of Hall of Fame eligibility. 

"This is the last time I'm ever getting on a scale," Mayweather told Showtime's Jim Grey following Friday's weigh-in. 

There are many in the industry who view this fight as the unbeaten pound-for-pound king going out with a whimper.

Don't tell that to his opponent, who insists that Mayweather is going home with a loss.

Berto is 3-3 in his past six starts, but has won two straight, including a 6th round knockout of Josesito Lopez in March. The former welterweight champ enters Saturday's fight as an 11-1 underdog, but the weigh-in comes just hours after Serena Williams—regarded as the top female tennis player in the world—suffered one of the biggest upsets in U.S. Open history as she was ousted from the semifinals following a three-set loss to unranked Roberta Vinci. 

Can lightning strike twice in one weekend? 

"Of course," Berto said of pulling off the upset. "God is good, so everyone tune in." 

The chief support is a rematch to one of the year's best fights, as Roman Martinez faces Orlando Salido in a super featherweight title fight.

Martinez weighed 129.5 lbs. for the first defense of his title, which he claimed from Salido in a 12-round thriller in April. Salido weighed in right at the 130 lb. limit.

In another fight featuring a newly crowned champion, Badou Jack faces mandatory challenger George Groves in a 12-round super middleweight title fight. 

Jack, born in Sweden but now fighting out of Las Vegas, tipped the scales at 167.5 lbs. Groves came in bang on the 168 lb. limit.

The bout marks the first defense of the title for Jack, who scored one of the year's biggest upsets with a 12-round majority decision win over previously unbeaten Anthony Dirrell in April. The feat extended his win streak to three straight folllowing the lone loss of his career, a shocking 1st round knockout at the hands of journeyman Derek Edwards last February.

Groves travels from jolly old England in search of his first championship. The top-rated contender enters his third career title fight. His previous two attemps resulted in the lone defeats on his ledger, suffering back-to-back stoppages to Carl Froch. He has since won two straight.

Opening the PPV telecast, former two-division champ Jhonny Gonzalez faces Jonathan Oquendo in a 10-round super featherweight bout. Both fighters weighed 129 lbs. 

Gonzalez fights for the second time in six weeks. The veteran slugger from Mexico rebounded from his title-losing knockout to Gary Russell Jr. in March with a 1st round knockout of Kazuki Hashimoto this past August. 

Oquendo is coming off of a 10-round win over Gabino Cota this past March. 

FULL WEIGHTS

Floyd Mayweather Jr, 146 lbs. vs. Andre Berto, 145 lbs.—12 rds, welterweight

Badou Jack, 167.5 lbs. vs. George Groves, 168 lbs.—12 rds, super middleweight

Roman Martinez, 129.5 lbs. vs. Orlando Salido, 130 lbs.—12 rds, super featherweight

Jhonny Gonzalez, 129 lbs. vs. Jonathan Oquendo, 129 lbs.—10 rds, super featherweight

Vanes Martirosyan, 154.5 lbs. vs. Ishe Smith, 154 lbs.—10 rds, super welterweight

Christopher Pearson vs. Janks Trotter—10 rds, middleweight

Ronald Gavril vs. Scott Sigmon—10 rds, super middleweight

Ashley Theophane vs. Steve Upsher Chambers—10 rds, super lightweight

Gervonta Davis vs. Recky Dulay—8 rds, super featherweight

Sanjarbek Rakhmanov vs. Farkhad Sharipov—6 rds, super lightweight

Trakwon Pettis vs. Devante Seay—4 rds, super lightweight

Jake Donovan is the managing editor of BoxingScene.com

Twitter: @JakeNDaBox

Facebook Page: JakeBScene