British light heavyweight Joshua Buatsi earned a win yet unimpressive debut to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a tight 10-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective individual punches in a contest where the styles didn't complement each other, with excessive holding marring the fight.
The scoring judges judged it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest display but what do champions do? They win," Buatsi stated in the arena as he was greeted with negative reactions from the audience.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, deserved the win but the Derbyshire fighter experienced the second defeat of his 28-fight career.
The Champion Secures Win in Slow Affair
The fighter's advancement has plateaued in recent times through management issues and considerable time of inactivity.
Previously predicted as the future of British boxing, he now finds himself trying to realize his potential - perhaps in what feels like a final roll of the dice - under fresh management.
He started carefully, with the two boxers willing to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand during the bout, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who worked behind a protective stance to barely take the cleaner periods.
The audience's tolerance diminished amid regular grabbing, with Parker slipping to the canvas various instances during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. However, ex-champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Arthur beat Bradley Rea by divided decision in a excellent Manchester vs Manchester fight to secure the European light heavyweight title.
The arena became quiet for a profoundly moving homage prior to the bout as 10 bells sounded in remembrance of Manchester's own Ricky Hatton, who died aged 46 in September.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime ended, the quiet gave way to a roar of "there's only one Ricky Hatton".
The action during the bout matched the sentiment. The eventual winner was knocked down by a powerful punch directly to the chin in the initial stage, getting up unsteadily to his position on the referee's count.
But the traditional red shorts of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was marked up early, noticeable damage appearing under his eye as the pair landed powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, 34, matched the intensity with stinging uppercuts as the action rarely dropped over the full distance.
The victor edged the decision with official scores of even score, narrow lead and wider gap, but both fighters were relentless and full of heart, all the qualities their inspiration the legend embodied.
