British light heavyweight Joshua Buatsi made a winning yet disappointing start to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a tight 10-round bout at the boxing arena.
But Parker landed significant shots, landing some telling individual punches in a match where the approaches never quite clicked, with frequent clinching disrupting the action.
The scoring judges judged it 96-94 to the winner, with the final judge a even score.
"It wasn't my greatest performance but what do champions do? They succeed," the victor stated in the ringside as he was faced disapproval from the crowd.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Various analysts believed the challenger, thirty-one, should have been awarded the decision but the contender endured the second setback of his 28-match professional journey.
The Champion Earns Triumph in Slow Encounter
Buatsi's progress has plateaued in recent years through promotional disputes and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now finds himself trying to achieve expectations - possibly in what appears to be a last chance - under recent support.
He opened tentatively, with both competitors willing to be aggressive in a cagey opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was participating in his second fight at the higher weight class.
By the middle rounds, the underdog had made it competitive, causing problems for Buatsi, who operated with a solid defense to edge the more effective periods.
The crowd's patience wore thin during regular grabbing, with Parker slipping to the canvas various instances during clinches.
The underdog closed well, but several stanzas were difficult to score. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Memorial Fuels All-Manchester Fight
In the co-main event, Arthur defeated Rea by split-decision in a terrific Manchester vs Manchester fight to secure the European light-heavyweight title.
The stadium fell silent for a deeply poignant memorial prior to the bout as ten bells sounded in memory of local hero Hatton, who succumbed 46 years old in recently.
It was the first major televised fight night in the city since Hatton's passing. As the last bell ended, the silence gave way to a roar of "there's only one Hatton".
The action inside the ropes equaled the emotion. The eventual winner was sent to the canvas by a significant blow directly to the jaw in the early round, getting up unsteadily to his footing on the eight count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. From the other corner, Rea - in rival City blue - was injured quickly, heavy swelling forming under his eye as the fighters traded powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
Arthur barely secured the decision with official scores of draw, close margin and 115-112, but both fighters were relentless and full of heart, all the qualities their inspiration Hatton stood for.
