UK light heavyweight Joshua Buatsi earned a win yet disappointing debut to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a tight 10-round contest at the Manchester venue.
But Parker landed significant shots, delivering effective single shots in a fight where the styles never quite clicked, with excessive holding marring the action.
The scoring judges had it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," the victor said in the arena as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in February - to secure a 20th career victory.
Various analysts thought the challenger, thirty-one, deserved the decision but the British boxer endured the second defeat of his 28-bout professional journey.
Buatsi Earns Triumph in Dull Match
The fighter's advancement has stalled in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now finds himself trying to realize his potential - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with both competitors prepared to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second fight at the higher weight class.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who utilized a tight guard to narrowly win the cleaner rounds.
The crowd's patience diminished during regular grabbing, with Parker going down various instances during grappling.
Parker closed well, but multiple periods were difficult to score. Nevertheless, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi moves on, but with the likes of hard hitter Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Arthur beat Rea by split-decision in a outstanding all-Manchester contest to capture the continental championship.
The stadium became quiet for a deeply poignant homage before the fight as ten bells sounded in memory of Manchester's own Hatton, who died aged 46 in recently.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound faded, the silence gave way to a roar of "only one Ricky Hatton".
The action during the bout reflected the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the face in the early round, rising shakily to his feet on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was injured quickly, noticeable damage developing under his eye as the fighters traded powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the intensity hardly diminished over twelve rounds.
The victor barely secured the decision with official scores of draw, close margin and clearer margin, but the two athletes were persistent and full of heart, all the qualities their inspiration Hatton stood for.
