UK light heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a split decision in a close 10-round fight at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a match where the approaches failed to mesh, with frequent clinching disrupting the contest.
Two judges scored it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the arena as he was faced negative reactions from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers felt Parker, thirty-one, merited the decision but the Derbyshire fighter experienced the second setback of his 28-match career.
The Champion Secures Victory in Dull Encounter
His career development has plateaued in recent times through contract problems and considerable time of inactivity.
Once tipped as the next star of the British fight scene, he now stands trying to fulfil that early promise - maybe in what feels like a ultimate opportunity - under fresh management.
He started carefully, with both competitors prepared to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after breaking his hand mid-fight, was making just his second fight at light heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the more effective stanzas.
The audience's tolerance decreased because of frequent holding, with the challenger going down several times during grappling.
Parker ended stronger, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Fuels Manchester Derby Contest
In the co-main event, Arthur defeated Bradley Rea by split-decision in a excellent Manchester vs Manchester contest to capture the European light-heavyweight title.
The arena became quiet for a deeply poignant homage prior to the bout as 10 bells rang in honor of local hero Ricky Hatton, who died aged 46 in recently.
It was the first major televised match card in the location since Hatton's death. As the last bell faded, the stillness transitioned to a shout of "there's just one Ricky Hatton".
The fighting within the ring reflected the emotion. The eventual winner was sent to the canvas by a significant blow flush on the face in the initial stage, standing uncertainly to his feet on the eight count.
But the Manchester United-red equipment of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was damaged early, heavy swelling developing under his eye as the duo traded hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur edged the result with judges scorecards of 114-114, 115-113 and wider gap, but both fighters were determined and brave, everything their hero Hatton represented.
