ONE Fight Night 21 results: Kade Ruotolo chokes out Francisco Lo after tough test

This should serve as notice to all of Kade Ruotolo's future opponents: all he needs is a split-second opening to choke you out.

Ruotolo, the reigning ONE lightweight submission grappling world champion, took on his toughest test in ONE Championship yet, in the form of Brazil's 'Chico' Francisco Lo. And the 21-year-old phenom scored his most exciting finish yet.

The two locked horns in a non-title 180-pound catchweight submission grappling match at ONE Fight Night 21: Eersel vs. Nicolas on Prime Video, which took place live at the iconic Lumpinee Boxing Stadium on Saturday morning in Bangkok, Thailand.

Heading into the contest, there were a lot of questions surrounding the matchup. Lo was presented as a legitimate threat, Ruotolo's biggest test in the world's largest martial arts organization. On top of that, fans wondered if Ruotolo's mind was on other things -- he is scheduled to make his much-awaited mixed martial arts debut in June at ONE 167.

In the first half of the grappling contest, Lo proved to be a formidable opponent. The Brazilian was aggressive with his attacks, exploding for flying triangles, jumping for body locks, and putting Ruotolo on the defensive.

However, a momentary lapse of concentration from Lo gave Ruotolo the opportunity he needed, and the American capitalized. Ruotolo swiftly took the back of his Brazilian opponent, slid his forearm underneath the chin, and found the rear-naked choke to force the tap.

The official finish came at the 4:48 minute mark.

As with all of Ruotolo's matches, speed was once again the killer in this one. A split-second moment was all it took.

What's next for Kade Ruotolo?

ONE lightweight submission grappling world champion Kade Ruotolo will make his professional MMA debut at ONE 167 on Prime Video. He will face fellow American Blake Cooper in a lightweight contest.

The event broadcasts live from the Impact Arena in Bangkok, Thailand. Fans in the United States and Canada can catch all the action live and for free on June 7th, U.S. primetime, via Amazon Prime Video