British light heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a close 10-round fight at the boxing arena.
But the challenger had his moments, landing some telling clean blows in a fight where the techniques never quite clicked, with frequent clinching marring the fight.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but what do champions do? They win," the victor said in the ring as he was greeted with boos from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th pro success.
Several boxing experts felt the challenger, thirty-one, merited the victory but the British boxer experienced the second loss of his 28-match career.
The Champion Secures Win in Uneventful Affair
Buatsi's progress has slowed in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of UK boxing, he now stands trying to realize his potential - perhaps in what feels like a last chance - under fresh management.
He opened tentatively, with neither fighter prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was participating in his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who worked behind a solid defense to edge the better rounds.
The crowd's patience wore thin because of regular grabbing, with the challenger falling to the floor multiple occasions during grappling.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Tribute Inspires All-Manchester Battle
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester battle to capture the European light heavyweight title.
The arena became quiet for a deeply poignant tribute prior to the bout as ten bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away 46 years old in September.
It was the premier televised boxing event in the location since Hatton's death. As the last bell faded, the quiet became a chant of "there's only one Hatton".
The fighting during the bout matched the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the chin in the initial stage, getting up unsteadily to his footing on the referee's count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was marked up soon, significant bruising appearing under his eye as the fighters exchanged hard punches.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with effective uppercuts as the intensity hardly diminished over twelve rounds.
The victor narrowly won the decision with judges scorecards of even score, 115-113 and 115-112, but the two athletes were persistent and courageous, everything their hero the legend stood for.
