British light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a tight ten-round fight at the Manchester venue.
But the challenger had his moments, landing some telling individual punches in a contest where the approaches didn't complement each other, with frequent clinching marring the contest.
The officials scored it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They win," the victor stated in the ring as he was greeted with disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Various analysts believed Parker, thirty-one, merited the victory but the Derbyshire fighter suffered the second loss of his 28-fight career.
Buatsi Claims Win in Slow Match
Buatsi's progress has stalled in recent years through management issues and extended periods of lack of fights.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a last chance - under fresh management.
He started carefully, with both competitors willing to overcommit in a cagey early stages.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand mid-fight, was competing in only his second fight at light heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to barely take the more effective rounds.
The crowd's patience wore thin amid constant clinching, with the challenger going down several times during close exchanges.
The underdog closed well, but many rounds were challenging to assess. Although, former world champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
The victor advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Tribute Motivates All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the European light heavyweight title.
The arena fell silent for a profoundly moving tribute prior to the bout as a bell ceremony sounded in honor of local hero Hatton, who died 46 years old in recently.
It was the first major televised match card in the urban center since the passing of Hatton. As the final chime disappeared, the silence became a shout of "there's only one Hatton".
The action during the bout reflected the sentiment. Arthur was floored by a significant blow directly to the face in the initial stage, rising shakily to his position on the referee's count.
But the traditional red shorts of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was damaged early, noticeable damage appearing under his orbital area as the duo traded powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace hardly diminished over the full distance.
Arthur narrowly won the decision with judges scorecards of even score, close margin and wider gap, but each competitor were persistent and courageous, everything their inspiration Hatton stood for.
