British light heavyweight Joshua Buatsi earned a win yet underwhelming start to life under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a competitive ten-round contest at the Manchester venue.
But the challenger landed significant shots, landing some telling clean blows in a match where the styles didn't complement each other, with constant grabbing spoiling the fight.
The officials scored it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my greatest display but what defines champions? They win," Buatsi commented in the arena as he was met by negative reactions from the crowd.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th career victory.
Various analysts believed Parker, 31, should have been awarded the win but the Derbyshire fighter endured the second setback of his 28-fight career.
Buatsi Secures Victory in Dull Match
The fighter's advancement has plateaued in the past few years through contract problems and extended periods of inactivity.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - perhaps in what seems like a final roll of the dice - under fresh management.
He started carefully, with both competitors willing to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was participating in his second bout at light heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who operated with a solid defense to narrowly win the more effective stanzas.
The crowd's patience wore thin during constant clinching, with the challenger slipping to the canvas several times during grappling.
Parker closed well, but multiple periods were hard to judge. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the presence of heavy hitter David Benavidez, and Russian star Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a excellent local rivalry fight to secure the continental championship.
The venue became quiet for a deeply poignant tribute prior to the bout as a bell ceremony sounded in remembrance of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the first major televised fight night in the urban center since the passing of Hatton. As the last bell disappeared, the quiet became a roar of "there's just one Ricky Hatton".
The fighting during the bout reflected the emotion. Arthur was knocked down by a significant blow flush on the jaw in the early round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of Arthur soon came forward again. From the other corner, Rea - in rival City blue - was marked up quickly, significant bruising developing under his face as the fighters landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the action rarely dropped over 12 rounds.
The victor edged the result with judges scorecards of even score, narrow lead and wider gap, but each competitor were determined and courageous, all the qualities their idol the legend stood for.
