America's best boxer Errol Spence Jr. vows to send Manny Pacquiao 'into retirement' when they fight August 21

• Errol Spence Jr. fights Manny Pacquiao on August 21.
• The match pairs a new attraction against one of the most successful pay-per-view fighters ever.
• Spence Jr. has vowed to knock 42-year-old Pacquiao into retirement.

America's best boxer Errol Spence Jr. has vowed to send Manny Pacquiao "into retirement" when they fight August 21 at a yet-to-be-determined location in Las Vegas.

Unbeaten welterweight champion Spence Jr. is building an impressive boxing resume in the 147-pound division with victories over Kell Brook, Lamont Peterson, Mikey Garcia, Shawn Porter, and Danny Garcia.

But later this summer the 31-year-old takes on his most accomplished opponent to date when Filipino fighter Pacquiao returns to the ring for his first fight in two years.

In 71 fights, Pacquiao has won championships in eight different weight classes - a boxing record. He won his first world title aged 20 in 1999, and has held a championship in every decade since. In his 71 fights, Pacquiao has amassed a record of 62 wins (39 knockouts) to seven defeats (three knockouts) and two draws.

But Spence Jr. is determined to produce the fight of his life so that he can finish Pacquiao on the night, and bring to an end one of the sport's greatest careers.

"I'm preparing my body to get into training camp mode and do the best that I can, to get into the best shape that I can, and be as strong as I can, to knock out Manny Pacquiao and send him off into retirement," Spence told YouTube channel Barbershop Conversations.

Spence Jr. is one of the best fighters operating in boxing today, according to Insider's pound-for-pound ranking.

As an already-established pay-per-view fighter, represented by Premier Boxing Champions, this summer's Box Office showdown could go one of two possible ways.

Either Pacquiao, the legendary 42-year-old, rolls back the years for what would be one of his greatest victories. Or, a passing-of-the-torch moment occurs as the new generation's pay-per-view star defeats the last generation's.

Spence Jr. said he expects "the same Manny Pacquiao that we get every time" but that seemingly does not deter him from pursuing an early victory.