Saul “Canelo” Alvarez’s win over Christian Mbilli has been marred by a sickening knockout on his undercard.

Mexican legend Canelo, 36, claimed a 17th world title of his iconic 69-fight professional career with a unanimous decision victory against Frenchman Christian Mbilli in Riyadh on Sunday morning (AEST).

Watch the devastating KO via the video player above

Be the first to know when news breaks. Download our new app

The triumph sees Canelo reclaim the WBC Super Middleweight crown, but that was not the headline moment from the night.

Gallen v Asofa-Solomona | Friday November 6 from 7pm AEDT | Australian sporting icon and crossover boxing king Paul Gallen returns to the ring to face his biggest opponent yet, Nelson ‘Big Nasty’ Asofa-Solomona. | Order now on Kayo Sports.

Instead, Canelo’s stablemate Bek Nurmaganbet scored a scary KO win over Alvarez’s compatriot Marcos Vazquez Rodriguez.

Undefeated Nurmaganbet, 28, who moves to 17-0, poleaxed Vazquez with three seconds remaining of the opening round with two devastating short hooks.

The referee immediately waved off the contest as Vazquez laid motionless underneath the ropes.

There has been no official update on Vazquez’s condition, but according to Mexican media reports he received medical attention and oxygen during the aftermath of the bout.

It is understood he left the ring unaided after receiving treatment.

The commentators on DAZN referred to the finish as “dangerous” and described Vazquez as being “out cold”.

Fans on social media also reacted in their droves, with Chris Machado saying: “Damn, that’s some vicious power!”

Cyprus Isles Fans added: “That was absolutely brutal, I had to watch it three times, honestly.”

Play Elevyn responded: “See ya later. Wow.”

And Superbeast MMA said: “KNOCKOUT OF THE YEAR CONTENDER?!”

The knockout is Nurmaganbet’s 15th in 17 fights — and his 13 successive stoppage victory as he continues to grow his reputation as a concussive puncher.

Canelo win marred by ‘dangerous’ undercard KO

Meanwhile, four-weight world champion Canelo got the nod on all three judges scorecards against Mbilli as they ruled it 116-111, 117-110 and 115-112 in favour of the Mexican superstar.

It is his first fight since losing to Terence Crawford in September last year, and he now holds a record of 61 wins, three defeats and two draws.

Following the fight, he called for a rematch with Crawford — who retired after his win over Canelo.

Alvarez said: “Hopefully, yes (we can do the rematch). We would honestly love to have that rematch, like I’ve told you.

“If not, we’ll keep moving forward with our career, but hopefully that fight can happen.”