[1] On May 21, 2021, former eight-division world champion Manny Pacquiao made the unexpected announcement on his social media that he would face undefeated WBC and IBF welterweight champion Errol Spence Jr. on August 21 in Las Vegas on Fox pay-per-view (PPV).

[2] Premier Boxing Champions and Fox confirmed the news, and it was reported that both men have signed contracts to face each other.

[6] On August 10, it was announced that Spence would be replaced by WBA (Super) champion Yordenis Ugás, after being forced to pull out of the bout with Pacquiao due to suffering an injury to his left eye.

[7] Professional wrestling promotion WWE hosted their annual SummerSlam pay-per-view event on the same night at the nearby Allegiant Stadium, which raised concerns over whether or not fans would be able to attend or watch both shows.

[8] WWE had planned to have SummerSlam end with enough time for fans to leave the Allegiant Stadium and make it over to the T-Mobile Arena to watch the main event fight between Pacquiao and Ugás, or for those watching at home, enough time to switch PPV channels.