British light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to life under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive ten-round fight at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful clean blows in a fight where the approaches failed to mesh, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," Buatsi commented in the ringside as he was greeted with negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a 20th pro success.
Some ringside observers believed Parker, thirty-one, deserved the decision but the British boxer endured the second loss of his 28-match career.
Buatsi Secures Win in Slow Match
His career development has slowed in recent years through management issues and extended periods of inactivity.
Once tipped as the future of British boxing, he now stands trying to realize his potential - perhaps in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers willing to take risks in a cagey early stages.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was making just his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who utilized a tight guard to edge the better rounds.
The audience's tolerance wore thin because of constant clinching, with the challenger slipping to the canvas various instances during clinches.
The underdog ended stronger, but several stanzas were difficult to score. Although, ex-champion Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Homage Motivates All-Manchester Battle
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry fight to capture the European light-heavyweight title.
The stadium fell silent for a extremely emotional tribute before the fight as ten bells rang in memory of local hero Hatton, who succumbed at age 46 in September.
It was the first major televised match card in the location since Hatton's death. As the concluding sound ended, the silence gave way to a shout of "there's just one Hatton".
The competition inside the ropes matched the feeling. Arthur was knocked down by a significant blow flush on the face in the second round, getting up unsteadily to his position on the eight count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was injured soon, heavy swelling forming under his face as the fighters traded hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the pace rarely dropped over twelve rounds.
The victor edged the decision with scoring tallies of even score, 115-113 and clearer margin, but the two athletes were relentless and brave, everything their inspiration Hatton stood for.
