Once more unto the breach, dear fight fans. You might think paraphrasing Henry V is too froufrou to apply to the pugilistic arts, but this bout is a bit Shakespearean in dimension.

Boxing’s reigning king of the ring—Floyd Mayweather Jr., owner of a flawless 48-0 record with 26 knockouts over 19 years—will venture back into the MGM Grand Garden Arena for fist-to-fist combat when he takes on two-time welterweight world champion Andre Berto (30-3, with 23 knockouts) in what Mayweather says will be his final fight.

What’s at stake is inclusion in the history books alongside a legend. With this contest, Mayweather aims to match the record of the late, lionized heavyweight champ, Rocky Marciano, who retired in 1956 with a pristine, 49-0 record (though Marciano far outdistanced him on knockouts with 43.)

In May, in a bout generating more than $500 million in revenue, Mayweather defeated Manny Pacquiao in a unanimous decision. Since then, some critics and fans have hammered Mayweather for choosing Berto as his final opponent, claiming he is a safe, more easily beatable choice than other challengers.

However, in Berto (nickname: The Beast), 38-year-old Mayweather faces a 32-year-old opponent, a power puncher with a high-punch output and strong hand speed who should prove a challenge to the champ’s signature defense and speed. Another adjective applied to Berto: hungry. And eager to pull off an historic upset.

Skeptics suggest that should Mayweather claim his record-tying 49th victory without a loss, he won’t be able to resist postponing retirement to go for No. 50 to sit alone atop the throne. A king refusing to share his kingdom? Shakespearean, indeed.

MGM Grand, 3 p.m. Sept. 12, ticket prices vary. 800.745.3000 Ticketmaster