British light heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a majority decision in a tight ten-round fight at the boxing arena.
But Parker had his moments, delivering effective single shots in a match where the techniques never quite clicked, with constant grabbing disrupting the action.
Two judges judged it 96-94 to the winner, with the third a 95-95.
"It wasn't my finest performance but how do champions respond? They win," the victor said in the ring as he was greeted with negative reactions from the crowd.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts thought Parker, thirty-one, deserved the decision but the contender endured the second loss of his 28-bout professional journey.
The Champion Secures Victory in Slow Encounter
The fighter's advancement has slowed in recent times through contract problems and long spells of lack of fights.
Previously predicted as the next star of British boxing, he now stands trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under recent support.
He began cautiously, with neither fighter willing to take risks in a tentative opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who utilized a solid defense to narrowly win the cleaner rounds.
The spectators' acceptance diminished during constant clinching, with Parker falling to the floor multiple occasions during clinches.
Parker finished the stronger, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor moves on, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Lyndon Arthur defeated Bradley Rea by split-decision in a terrific Manchester vs Manchester fight to secure the European light-heavyweight belt.
The arena grew hushed for a extremely emotional tribute prior to the bout as a bell ceremony sounded in memory of local hero Hatton, who passed away 46 years old in September.
It was the initial significant broadcast fight night in the location since the passing of Hatton. As the concluding sound disappeared, the quiet transitioned to a shout of "only one Ricky Hatton".
The fighting within the ring reflected the sentiment. Arthur was sent to the canvas by a powerful punch flush on the jaw in the second round, getting up unsteadily to his feet on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was injured early, noticeable damage developing under his orbital area as the duo landed punishing blows.
The challenger, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace seldom decreased over the full distance.
Arthur barely secured the verdict with scoring tallies of even score, 115-113 and wider gap, but the two athletes were persistent and courageous, all the qualities their hero the legend embodied.
