UK light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But the challenger found success, connecting with powerful single shots in a match where the techniques never quite clicked, with frequent clinching spoiling the action.
The scoring judges had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor stated in the ringside as he was greeted with boos from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Various analysts believed Parker, 31, merited the win but the contender experienced the second loss of his 28-bout career.
The Champion Secures Win in Uneventful Affair
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors prepared to take risks in a calculated early stages.
Parker, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who utilized a tight guard to narrowly win the more effective rounds.
The spectators' acceptance wore thin during frequent holding, with Parker falling to the floor various instances during clinches.
Parker ended stronger, but several stanzas were hard to judge. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the caliber of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Fight
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester battle to secure the European light heavyweight championship.
The arena fell silent for a extremely emotional homage before the fight as ten bells tolled in remembrance of local hero Hatton, who succumbed at age 46 in recently.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell faded, the silence transitioned to a chant of "there's only one Hatton".
The fighting inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a significant blow flush on the jaw in the second round, standing uncertainly to his footing on the eight count.
But the Manchester United-red shorts of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was damaged soon, heavy swelling forming under his orbital area as the pair exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur narrowly won the result with judges scorecards of draw, 115-113 and 115-112, but both fighters were relentless and courageous, exactly what their hero the legend stood for.
