Frank Martin and Errol Spence Jr., Martin’s promoter, fulfilled the promise they made after he stopped Jackson Marinez almost four months ago, that the emerging lightweight would fight whichever opponent was willing to take the risk next.

BoxingScene.com has learned that Martin and Michel Rivera have agreed to meet in a high-stakes 135-pound fight December 17 at a venue to be announced. The lightweight bout between Indianapolis’ Martin (16-0, 12 KOs) and the Dominican Republic’s Rivera (24-0, 14 KOs) will be the main event of a “Showtime Boxing: Special Edition” telecast that night.

The card headlined by Martin-Rivera is expected to be held at The Armory in Minneapolis, where David Morrell Jr. (7-0, 6 KOs) will defend his WBA world super middleweight title against Aidos Yerbossynuly (16-0, 11 KOs) on Saturday night in a “Showtime Championship Boxing” main event.

The 27-year-old Martin, a southpaw from Indianapolis, is eager to prove himself against an undefeated fighter.

He conquered another Dominican lightweight in Marinez (20-3, 8 KOs), whom Martin dropped in the ninth and 10th rounds on his way to a 10th-round, technical-knockout victory July 9 at Alamodome in San Antonio. Martin was ahead by scores of 88-82, 88-82 and 87-83 entering the 10th round against Marinez.

Showtime aired Martin-Marinez as part of the Rey Vargas-Mark Magsayo undercard July 9.

Martin is trained by Derrick James, who has guided Spence, the unbeaten IBF/WBA/WBC welterweight champion, throughout his career.

The 24-year-old Rivera, an orthodox boxer who is trained by Herman Caicedo in Miami, most recently out-boxed Jerry Perez (14-2, 11 KOs) to secure an eight-round, unanimous-decision win on the Deontay Wilder-Robert Helenius undercard October 15 at Barclays Center in Brooklyn. All three judges credited Rivera for a decisive victory over Perez (80-71, 79-72, 79-72), which was broadcast by FS1.

In his prior appearance, Rivera out-pointed previously unbeaten Joseph Adorno (17-1-2, 14 KOs) in a 10-rounder Showtime televised as the opener of a tripleheader March 26 from The Armory. The craftier Rivera defeated Adorno by the same score, 97-93, on all three cards.

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