Alexander Povetkin broke the hearts of David Price and the Principality Stadium after delivering a savage couple of hooks to end proceedings.
Round three witnessed Price on the floor before the Liverpudlian bounced back to leave the Russian hanging on the ropes and take a standing eight count which saw Cardiff erupt.
But the fairytale wasn’t to be as Price appeared unconscious on the canvas in round five.
The medical team treated the courageous Brit immediately before the heavyweight was back up on his feet.
Povetkin will now be hoping to be the next in line to challenge the winner of Anthony Joshua and Joseph Parker.
Belfast bantamweight Ryan Burnett retained his WBA title, defeating mandatory challenger Yonfrez Parejo 120-108 120-108 116- 112.
The Adam Booth fighter never looked in doubt with his Venezuelan opponent often refusing to engage in any trade.
Burnett admitted he is open to a showdown against the winner of Naoya Inoue and Jamie McDonnell.
Ex-world champion Anthony Crolla overcame a deep cut above his left eye to win a second successive fight and continue his quest for another tilt at world glory.
Crolla suffered the cut following a clash of heads and was forced to produce a patient, dogged performance.
‘Million Dollar’ inflicted the first defeat to the record of Edson Ramirez, with all three judges scoring the fight in favour of the Mancunian (100-91, 100-90, 98-92).
Josh Kelly overcame a durable test in Carlos Molina as he cruised to a unanimous points victory to claim the vacant WBA International welterweight title.
The North East boxer grabbed some vital ring experience, going the full ten-round distance to win on the scorecards 98-92, 98-91 and 99-91.
Kelly said after the fight: “I didn’t want to hurt the hands, I know Eddie has big plans for June.”
Eddie Hearn confirmed his next move for ‘Pretty Boy’ Kelly, he added: “We’re going to have a party in Newcastle. June 16 he’s coming home and it’s going to be a big night. He’s going all the way.”
Joe Hewlett is lead writer for World Boxing News. Follow Joe on Twitter @Hewlett95