​Damian Knyba lands a punch on Andy Ruiz Jr during their heavyweight bout at the Prudential Center in Newark on Friday night.Photograph: Ed Mulholland/Getty ImagesAndy Ruiz Jr’s comeback bid was left in tatters on Friday night after the former unified heavyweight champion was knocked down and picked apart in a sobering unanimous-decision defeat to Damian Knyba in Newark, New Jersey.Knyba won by scores of 117-110 and 114-113 twice, handing Ruiz the third defeat of his professional career and dealing a devastating blow to his hopes of becoming a two-time champion in boxing’s prestige division. The baffling pair of 114-113 cards flattered Ruiz considerably and bore little relation to the mostly one-way traffic that unfolded. (The Guardian had it 117-110.)“This feeling is so amazing,” the New Jersey-based Pole said afterwards through a translator. “Not many people in the world can feel what I’m feeling right now.”Ruiz (35-3-1, 22 KOs), who turns 37 next week and was returning from a 762-day layoff, cut a lamentable figure for most of the night, his once-blurring combinations carrying little of their old snap, his head almost stationary as the 30-year-old Knyba’s jab found it time and again. By the end of 12 dispiriting rounds at the home of the NHL’s New Jersey Devils, he looked less like a contender launching one final climb toward the summit than a shot fighter badly compromised by inactivity and injury.Seven years ago, Ruiz authored one of the greatest upsets in boxing history at Madison Square Garden, climbing off the canvas to knock down the undefeated Anthony Joshua four times before stopping him in the seventh round and becoming the first fighter of Mexican descent to win a world heavyweight title. Barely six months later, the fairy tale was over. After months of partying and an abbreviated training camp, Ruiz arrived for the rematch 15lb heavier and surrendered the titles back to Joshua in a listless points defeat in Saudi Arabia, ending his unlikely reign after just 190 days.For Ruiz, who had fought only three times in more than six years, Friday was meant to mark the beginning of one last run at a title suddenly within reach with 39-year-old Oleksandr Usyk preparing to exit the stage. Instead, Ruiz spent most of the night plodding after the 6ft 7in Knyba, unable to access the hand speed or footwork required to overcome the enormous physical disparity. There was little power behind his punches and even less of the explosive drive through his legs that once gave them such menace, perhaps a consequence of his surgically repaired right knee.For six rounds it was a dour display. Knyba established the pattern early with a long, pawing left jab while moving backward, content to concede ground without allowing Ruiz into punching range. Whenever Ruiz did close the distance, the Pole swallowed him up with his 86in reach and waited for referee David Franciosi to separate them. Ruiz trudged forward with almost no head movement, struggl