UK light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a tight 10-round fight at the boxing arena.
But Parker found success, landing some telling clean blows in a contest where the techniques failed to mesh, with excessive holding disrupting the action.
The officials had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what do champions do? They succeed," the victor commented in the arena as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts felt Parker, 31, merited the decision but the Derbyshire fighter suffered the second loss of his 28-fight career.
The Champion Secures Triumph in Dull Affair
Buatsi's progress has slowed in the past few years through management issues and considerable time of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to achieve expectations - possibly in what feels like a final roll of the dice - under recent support.
He began cautiously, with both competitors willing to overcommit in a cagey opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second bout at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for the favorite, who utilized a protective stance to edge the better rounds.
The spectators' acceptance diminished amid constant clinching, with Parker going down multiple occasions during clinches.
Parker ended stronger, but many rounds were difficult to score. However, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Hatton Memorial Motivates All-Manchester Contest
In the co-main event, Arthur beat Rea by split-decision in a terrific all-Manchester fight to capture the European light-heavyweight belt.
The stadium grew hushed for a profoundly moving homage before the fight as ten bells sounded in remembrance of the city's native Ricky Hatton, who died aged 46 in last month.
It was the first major televised fight night in the urban center since Hatton's passing. As the concluding sound faded, the quiet became a chant of "only one Ricky Hatton".
The fighting within the ring matched the emotion. The eventual winner was sent to the canvas by a left hook flush on the jaw in the initial stage, standing uncertainly to his footing on the eight count.
But the Manchester United-red attire of Arthur soon advanced again. From the other corner, Rea - in opposing blue - was damaged early, noticeable damage appearing under his face as the fighters landed punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action seldom decreased over 12 rounds.
The victor narrowly won the verdict with judges scorecards of draw, close margin and clearer margin, but both fighters were persistent and courageous, everything their hero the legend represented.
