British light-heavyweight Joshua Buatsi made a winning yet underwhelming start to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight ten-round contest at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a fight where the techniques never quite clicked, with frequent clinching spoiling the contest.
Two judges judged it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi commented in the ring as he was met by disapproval from the audience.
The British fighter returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts felt Parker, 31, deserved the decision but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
Buatsi Secures Victory in Slow Affair
The fighter's advancement has slowed in recent times through promotional disputes and extended periods of lack of fights.
Previously predicted as the future of the British fight scene, he now stands trying to realize his potential - perhaps in what seems like a last chance - under fresh management.
He opened tentatively, with both competitors prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after breaking his hand during the bout, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who utilized a protective stance to edge the cleaner stanzas.
The spectators' acceptance wore thin because of frequent holding, with the challenger falling to the floor various instances during clinches.
Parker closed well, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Inspires All-Manchester Contest
In the secondary fight, Arthur beat Rea by split-decision in a terrific Manchester vs Manchester battle to secure the European light heavyweight title.
The arena grew hushed for a extremely emotional memorial before the fight as a bell ceremony rang in honor of Manchester's own Hatton, who died aged 46 in recently.
It was the premier televised match card in the city since the passing of Hatton. As the final chime disappeared, the stillness transitioned to a chant of "only one Hatton".
The competition inside the ropes equaled the emotion. The eventual winner was knocked down by a powerful punch squarely on the jaw in the initial stage, rising shakily to his footing on the referee's count.
But the red-colored shorts of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was damaged early, noticeable damage developing under his eye as the pair landed powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the action rarely dropped over the full distance.
Arthur barely secured the decision with official scores of 114-114, narrow lead and wider gap, but each competitor were determined and brave, all the qualities their inspiration Hatton stood for.
