Eight years after Nonito Donaire’s loss to Guillermo Rigondeaux, “The Filipino Flash” has replaced Rigondeaux in a big fight.

BoxingScene.com has learned Donaire will face fellow Filipino champion John Riel Casimero in a bantamweight title unification fight August 14 at a site to be determined. Showtime will televise the 12-round bout between Donaire (41-6, 27 KOs), the WBC 118-pound champ, and Casimero (30-4, 21 KOs), the WBO titleholder, as the main event of a tripleheader.

Casimero-Rigondeaux was announced as part of Showtime’s four-month schedule of fights late in April.

Rigondeaux (20-1, 13 KOs, 1 NC) is not injured. Premier Boxing Champions’ Al Haymon simply decided to make a more intriguing, legitimate title unification bout between Donaire and Casimero.

The Cuban-born Rigondeaux likely will face an opponent to be determined on the Donaire-Casimero undercard. If Rigondeaux wins, the 40-year-old southpaw could challenge the Donaire-Casimero winner at a later date.

Rigondeaux hasn’t fought since he defeated Panama’s Liborio Solis (31-6-1, 14 KOs, 1 NC) by split decision in a 12-rounder 16 months ago at PPL Center in Allentown, Pennsylvania. The two-time Olympic gold medalist won the WBA’s secondary bantamweight belt by winning that bout, but Donaire-Casimero is a legitimate championship unification match.

Defeating Casimero would not only add another bantamweight title to Donaire’s collection, it could also give him an opportunity to avenge his loss to Rigondeaux. A then-unbeaten Rigondeaux overcame a 10th-round knockdown and defeated Donaire by unanimous decision in their 12-round, 122-pound title unification fight in April 2013 at Radio City Music Hall in New York.

The 38-year-old Donaire regained the WBC bantamweight championship he first won 10 years ago by knocking out previously undefeated French southpaw Nordine Oubaali (17-1, 12 KOs) in the fourth round May 29 at Dignity Health Sports Park in Carson, California. Donaire dropped Oubaali twice in the third round and once in the fourth round before their Showtime Championship Boxing main event was stopped.

The 32-year-old Casimero has made one defense of the WBO crown he won when he knocked out South Africa’s Zolani Tete (28-4, 21 KOs) in the third round of their November 2019 at Arena Birmingham in Birmingham, England.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.