UK light-heavyweight Joshua Buatsi secured a victory yet underwhelming debut to his career under recent management with a points victory over Parker in the Manchester arena.
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 found success, delivering effective clean blows in a fight where the approaches failed to mesh, with excessive holding disrupting the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but what do champions do? They succeed," Buatsi stated in the ring as he was met by negative reactions from the spectators.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in February - to earn a 20th career victory.
Various analysts believed the challenger, thirty-one, merited the decision but the British boxer experienced the second loss of his 28-match career.
Buatsi Claims Win in Uneventful Match
His career development has slowed in the past few years through contract problems and long spells of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter prepared to take risks in a calculated opening few rounds.
Parker, 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 halfway stage, the underdog had made it competitive, making life awkward for the favorite, who operated with a tight guard to narrowly win the better stanzas.
The audience's tolerance diminished because of regular grabbing, with Parker falling to the floor several times during grappling.
Parker finished the stronger, but several stanzas were hard to judge. Although, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the presence of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Contest
In the co-main event, Arthur overcame Rea by close verdict in a excellent Manchester vs Manchester contest to win the continental championship.
The stadium grew hushed for a extremely emotional memorial prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who succumbed at age 46 in recently.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the concluding sound faded, the silence became a roar of "only one Hatton".
The competition during the bout matched the sentiment. The eventual winner was knocked down by a left hook squarely on the face in the initial stage, getting up unsteadily to his position on the referee's count.
But the red-colored attire of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was injured soon, significant bruising appearing under his eye as the duo traded powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over the full distance.
The victor narrowly won the decision with official scores of even score, close margin and wider gap, but both fighters were relentless and courageous, exactly what their idol Hatton represented.
