UK light heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a tight 10-round contest at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a fight where the approaches failed to mesh, with constant grabbing disrupting the action.
The officials judged it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my best display but how do champions respond? They succeed," Buatsi stated in the arena as he was met by negative reactions from the spectators.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts felt the challenger, thirty-one, deserved the victory but the contender suffered the second setback of his 28-fight career.
Buatsi Earns Win in Dull Affair
His career development has slowed in the past few years through management issues and long spells of lack of fights.
Earlier forecast as the next star of UK boxing, he now stands trying to realize his potential - perhaps in what feels like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors prepared to take risks in a calculated initial rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury during the bout, was making just his second fight at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for the favorite, who operated with a tight guard to edge the more effective stanzas.
The crowd's patience decreased during constant clinching, with Parker slipping to the canvas various instances during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Although, former world champion Carl Frampton - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Arthur overcame Rea by close verdict in a outstanding all-Manchester fight to win the continental title.
The venue fell silent for a deeply poignant memorial prior to the bout as a bell ceremony rang in remembrance of Manchester's own Ricky Hatton, who succumbed aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the final chime ended, the silence gave way to a roar of "there's just one Ricky Hatton".
The fighting inside the ropes reflected the feeling. Arthur was sent to the canvas by a left hook flush on the face in the early round, rising shakily to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was injured soon, heavy swelling developing under his face as the duo exchanged hard punches.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over the full distance.
The victor edged the verdict with judges scorecards of 114-114, narrow lead and wider gap, but each competitor were persistent and brave, all the qualities their idol the legend represented.
