British light heavyweight Joshua Buatsi earned a win yet underwhelming start to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output likely gained him a majority decision in a close ten-round bout at the Manchester venue.
But the challenger landed significant shots, delivering effective clean blows in a fight where the approaches never quite clicked, with excessive holding marring the fight.
The officials judged it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi commented in the arena as he was met by boos from the crowd.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, thirty-one, merited the win but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
Buatsi Claims Triumph in Uneventful Affair
The fighter's advancement has plateaued in the past few years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to fulfil that early promise - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with neither fighter willing to overcommit in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second fight at light-heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the cleaner rounds.
The spectators' acceptance decreased because of constant clinching, with Parker falling to the floor various instances during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Hatton Tribute Inspires Manchester Derby Battle
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a outstanding local rivalry contest to capture the European light heavyweight title.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as ten bells rang in memory of local hero Hatton, who succumbed 46 years old in recently.
It was the premier televised match card in the city since Hatton's death. As the concluding sound disappeared, the silence transitioned to a shout of "only one Ricky Hatton".
The action during the bout equaled the feeling. The eventual winner was floored by a powerful punch squarely on the jaw in the early round, rising shakily to his footing on the eight count.
But the red-colored shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in rival City blue - was marked up soon, significant bruising appearing under his eye as the pair landed punishing blows.
Rea, 27, landed power punches but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace seldom decreased over 12 rounds.
The victor edged the decision with official scores of draw, narrow lead and wider gap, but the two athletes were determined and courageous, everything their inspiration Hatton represented.
