British light heavyweight Joshua Buatsi earned a win yet underwhelming debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a tight ten-round bout at the Manchester venue.
But Parker landed significant shots, connecting with powerful individual punches in a match where the techniques failed to mesh, with excessive holding marring the fight.
Two judges scored it 96-94 to the winner, with the third a even score.
"It wasn't my best display but how do champions respond? They succeed," the victor stated in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to earn a 20th career victory.
Various analysts thought Parker, 31, should have been awarded the victory but the contender experienced the second loss of his 28-bout career.
The Champion Secures Win in Dull Encounter
His career development has stalled in recent times through promotional disputes and long spells of inactivity.
Once tipped as the future of British boxing, he now stands trying to realize his potential - possibly in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers willing to be aggressive in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second appearance at light heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to narrowly win the better periods.
The crowd's patience decreased during frequent holding, with Parker going down various instances during grappling.
The underdog closed well, but multiple periods were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Hatton Memorial Inspires Manchester Derby Fight
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a excellent local rivalry battle to win the European light heavyweight title.
The venue fell silent for a profoundly moving tribute prior to the bout as ten bells tolled in remembrance of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised boxing event in the urban center since Hatton's passing. As the concluding sound faded, the stillness gave way to a chant of "only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was sent to the canvas by a significant blow squarely on the face in the second round, standing uncertainly to his footing on the referee's count.
But the red-colored attire of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was damaged quickly, heavy swelling forming under his orbital area as the pair traded powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over 12 rounds.
The victor edged the result with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were relentless and brave, all the qualities their idol Hatton embodied.
