British light heavyweight Joshua Buatsi earned a win yet underwhelming start to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a close ten-round fight at the Manchester venue.
But the challenger found success, connecting with powerful clean blows in a contest where the techniques didn't complement each other, with excessive holding spoiling the contest.
The scoring judges had it 96-94 for to Buatsi, with the third a even score.
"It wasn't my greatest performance but what defines champions? They succeed," the victor said in the arena as he was greeted with boos from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts thought Parker, 31, should have been awarded the victory but the contender suffered the second loss of his 28-bout professional journey.
Buatsi Earns Win in Dull Match
The fighter's advancement has slowed in recent years through management issues and extended periods of lack of fights.
Previously predicted as the next star of the British fight scene, he now is positioned trying to realize his potential - maybe in what feels like a last chance - under recent support.
He began cautiously, with both competitors willing to take risks in a cagey opening few rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after damaging his hand during the bout, was making just his second bout at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to edge the cleaner rounds.
The spectators' acceptance diminished during regular grabbing, with the challenger going down several times during close exchanges.
Parker ended stronger, but several stanzas were hard to judge. Although, ex-champion the boxing analyst - working with Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Fuels All-Manchester Contest
In the co-main event, Arthur defeated Rea by divided decision in a excellent Manchester vs Manchester contest to win the European light-heavyweight championship.
The stadium became quiet for a extremely emotional memorial prior to the bout as 10 bells tolled in memory of the city's native Hatton, who died at age 46 in September.
It was the first major televised boxing event in the city since Hatton's death. As the concluding sound faded, the quiet transitioned to a chant of "only one Ricky Hatton".
The competition within the ring equaled the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the jaw in the initial stage, rising shakily to his position on the eight count.
But the traditional red shorts of the fighter soon came forward again. Across the ring, the opponent - in opposing blue - was marked up soon, significant bruising forming under his eye as the pair traded powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action seldom decreased over the full distance.
Arthur edged the decision with official scores of 114-114, narrow lead and clearer margin, but both fighters were relentless and courageous, everything their hero Hatton embodied.
