British light-heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a tight 10-round fight at the Manchester venue.
But the challenger found success, delivering effective individual punches in a contest where the styles never quite clicked, with excessive holding disrupting the contest.
Two judges had it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my best display but how do champions respond? They succeed," the victor stated in the ringside as he was met by boos from the spectators.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th pro success.
Various analysts thought Parker, 31, should have been awarded the decision but the British boxer experienced the second loss of his 28-match career.
Buatsi Secures Triumph in Uneventful Encounter
The fighter's advancement has stalled in recent times through management issues and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to realize his potential - maybe in what appears to be a last chance - under fresh management.
He started carefully, with the two boxers prepared to overcommit in a calculated initial rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who worked behind a protective stance to narrowly win the more effective periods.
The audience's tolerance wore thin during regular grabbing, with the challenger going down multiple occasions during close exchanges.
The underdog finished the stronger, but multiple periods were hard to judge. Although, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just one round.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Hatton Tribute Motivates Local Rivalry Fight
In the supporting bout, Lyndon Arthur defeated Rea by split-decision in a terrific Manchester vs Manchester fight to win the European light-heavyweight championship.
The arena grew hushed for a profoundly moving tribute before the fight as ten bells sounded in memory of local hero Ricky Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the final chime faded, the stillness transitioned to a chant of "there's only one Hatton".
The fighting within the ring matched the sentiment. Arthur was floored by a significant blow directly to the jaw in the early round, rising shakily to his feet on the count of eight.
But the red-colored shorts of the fighter soon advanced again. From the other corner, the opponent - in competitive blue - was marked up early, heavy swelling appearing under his eye as the pair landed punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity rarely dropped over the full distance.
Arthur barely secured the verdict with scoring tallies of even score, 115-113 and 115-112, but both fighters were determined and full of heart, exactly what their hero Hatton stood for.
