UK light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a close 10-round bout at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a contest where the techniques never quite clicked, with excessive holding spoiling the action.
The scoring judges judged it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They prevail," the victor commented in the ringside as he was faced negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts believed the challenger, 31, merited the decision but the British boxer suffered the second defeat of his 28-match career.
The Champion Earns Triumph in Uneventful Encounter
The fighter's advancement has stalled in recent times through management issues and extended periods of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter willing to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who worked behind a tight guard to barely take the more effective periods.
The audience's tolerance decreased because of frequent holding, with Parker falling to the floor several times during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Although, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Tribute Inspires Manchester Derby Fight
In the supporting bout, Arthur beat Bradley Rea by divided decision in a outstanding all-Manchester battle to capture the continental title.
The stadium became quiet for a deeply poignant homage prior to the bout as a bell ceremony sounded in honor of local hero Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the last bell disappeared, the silence transitioned to a chant of "only one Ricky Hatton".
The action inside the ropes reflected the emotion. The eventual winner was floored by a significant blow directly to the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the traditional red shorts of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was damaged early, heavy swelling developing under his face as the fighters landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the decision with scoring tallies of 114-114, close margin and wider gap, but both fighters were persistent and full of heart, exactly what their hero Hatton represented.
