Brandon Rios to fight Diego Chaves

Welterweight Brandon Rios, having served a five-month suspension after testing positive for a banned substance after his last fight, will return to action on Aug. 2, promoter Top Rank announced on Wednesday.

Rios, a former lightweight titleholder, will face former interim welterweight titlist Diego Chaves in a scheduled 10-round bout in the main event of an HBO "Boxing After Dark" split-site tripleheader at The Cosmopolitan in Las Vegas.

The fight will be Rios' first since a near-shutout loss to Manny Pacquiao in November in Macau. Following the fight, Rios, who had agreed to random blood and urine testing by the Voluntary Anti-Doping Association, tested positive for the banned stimulant Methylhexanamine, which is often used as a dietary supplement but is also a performance-enhancing drug.

Rios (31-2-1, 23 KOs), 28, of Oxnard, California, will be looking to end a two-fight losing streak. Before the loss to Pacquiao, Rios dropped a unanimous decision in a rematch with Mike Alvarado for an interim junior welterweight belt in March 2013 in a strong fight of the year contender.

A third consecutive loss would be devastating to Rios' career and he knows it.

"This is a do or die fight for me," Rios said. "I know this fight is very important for my career. I am training extremely hard."

Chavez (23-1, 19 KOs), 28, of Argentina, is no walkover opponent. He is a powerful puncher who could give Rios problems. He won his most recent fight, a third-round knockout of Juan Alberto Godoy, in February but lost his interim belt in the previous fight when Keith Thurman knocked him out in the 10th round last July in San Antonio.

"I know that RĂ­os is a strong and difficult fighter. He is always a straight and a hard puncher," Chaves said. "I am very confident in my boxing skills and I think that with speed and mobility I will win."

Junior welterweight titlist Jessie Vargas (24-0, 9 KOs), 25, of Las Vegas, will make his first defense on the undercard when he faces Anton Novikov (29-0, 10 KOs), a 26-year-old southpaw from Russia.

"I cannot wait to be in the ring and perform in front of my hometown crowd," Vargas. "I am very happy that my first world title defense will be in my hometown and that my friends, family and fans will all be part of it."

Vargas claimed a 140-pound world title on April 12 on the Pacquiao-Timothy Bradley II undercard in Las Vegas by winning a debatable unanimous decision against Khabib Allakhverdiev.

While Rios-Chaves and Vargas-Novikov fight in Las Vegas, the HBO telecast will also include live coverage of light heavyweight titlist Sergey Kovalev (24-0-1, 22 KOs), 31, of Russia, making his third defense when he faces Australian southpaw Blake Caparello (19-0-1, 6 KOs) at the Revel Casino Hotel in Atlantic City, New Jersey.