UK light-heavyweight Joshua Buatsi made a winning yet unimpressive start to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a tight 10-round fight at the Co-op Live Arena.
But Parker had his moments, connecting with powerful individual punches in a fight where the styles never quite clicked, with excessive holding marring the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best display but how do champions respond? They succeed," Buatsi commented in the arena as he was met by negative reactions from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th pro success.
Various analysts felt the challenger, thirty-one, should have been awarded the decision but the British boxer endured the second loss of his 28-bout professional journey.
Buatsi Earns Win in Uneventful Affair
Buatsi's progress has slowed in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of the British fight scene, 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 neither fighter ready to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was making just his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, creating difficulties for the favorite, who operated with a protective stance to barely take the cleaner rounds.
The spectators' acceptance diminished during constant clinching, with Parker slipping to the canvas several times during close exchanges.
The underdog closed well, but several stanzas were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of heavy hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Hatton Tribute Motivates Local Rivalry Battle
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry contest to win the continental championship.
The arena became quiet for a deeply poignant homage prior to the bout as 10 bells tolled in memory of local hero Hatton, who died aged 46 in last month.
It was the premier televised boxing event in the location since Hatton's death. As the last bell ended, the silence transitioned to a chant of "there's only one Ricky Hatton".
The competition within the ring equaled the emotion. Arthur was knocked down by a left hook flush on the chin in the second round, getting up unsteadily to his feet on the referee's count.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was damaged early, heavy swelling forming under his eye as the pair landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the verdict with judges scorecards of even score, close margin and 115-112, but each competitor were determined and brave, all the qualities their inspiration Hatton represented.
