British light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a fight where the techniques never quite clicked, with excessive holding disrupting the action.
The officials had it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my best display but how do champions respond? They win," the victor stated in the ring as he was met by negative reactions from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to earn a 20th pro success.
Various analysts felt the challenger, 31, merited the decision but the contender suffered the second loss of his 28-match professional journey.
The Champion Secures Triumph in Slow Affair
His career development has stalled in the past few years through contract problems and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to realize his potential - maybe in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers prepared to take risks in a tentative early stages.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for the favorite, who operated with a tight guard to edge the more effective rounds.
The audience's tolerance wore thin because of regular grabbing, with the challenger slipping to the canvas various instances during close exchanges.
Parker finished the stronger, but multiple periods were challenging to assess. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur defeated Rea by split-decision in a terrific local rivalry contest to win the continental belt.
The venue grew hushed for a profoundly moving tribute ahead of the contest as a bell ceremony sounded in memory of the city's native Ricky Hatton, who passed away aged 46 in recently.
It was the initial significant broadcast match card in the location since Hatton's death. As the last bell faded, the stillness transitioned to a shout of "only one Hatton".
The action during the bout reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the face in the early round, standing uncertainly to his position on the count of eight.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged quickly, significant bruising developing under his orbital area as the fighters exchanged hard punches.
Rea, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over the full distance.
Arthur edged the decision with judges scorecards of draw, narrow lead and wider gap, but both fighters were relentless and full of heart, exactly what their hero Hatton embodied.
