Both fighters are coming off of submission victories in their last fights and will attempt to make it two-straight wins under the Ultimate Fighting Championship (UFC) banner.
Brazilian news outlet TATAME first reported the bout; however, UFC officials have yet to confirm the 155-pound contest.
Rio (9-1) had to wait nearly half a year to make his official UFC debut due to injuries after serving as a cast member on The Ultimate Fighter (TUF) season 15. The wait was worth it for the 31-year-old, though, as he picked up a hard-fought third-round submission victory over John Cofer at The Ultimate Fighter 16 Finale.
"The Wolverine" is a wrestling-based fighter who uses his ability to control opponent for (technical) knockout or submission victories, which he has earned in eight of his nine professional wins.
Trinaldo (12-2) has compiled a 2-1 record inside the Octagon thus far, finishing Delson Heleno and C.J. Keith while falling short against Gleison Tibau. "Massaranduba" was a cast member on TUF: Brazil where he was eliminated in the quarterfinal round.
The 34-year-old has fought all 14 of his professional and UFC bouts in his home country of Brazil. That trend will continue at UFC on FX 8.
Rio vs. Trinaldo will likely take place on the preliminary portion of the UFC on FX 8 fight card, which will air on Facebook and FUEL TV. The main card is scheduled to air on FX.
UFC on FX 8: "Belfort vs. Rockhold" goes down May 18, 2013, at Arena Jaragua in Jaragua do Sul, Santa Catarina, Brazil. The event headliner will see Vitor Belfort welcome Strikeforce middleweight champion Luke Rockhold to the organization in a five-round 185-pound contest. Also on the undercard, Constantinos Philippou and Ronaldo Souza have agreed to tangle.