UK light heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a competitive ten-round bout at the boxing arena.
But the challenger landed significant shots, landing some telling individual punches in a fight where the techniques never quite clicked, with excessive holding spoiling the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my finest showing but what defines champions? They prevail," the victor stated in the ring as he was faced boos from the spectators.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th pro success.
Various analysts thought the challenger, 31, should have been awarded the victory but the contender suffered the second loss of his 28-bout career.
The Champion Claims Triumph in Uneventful Match
His career development has slowed in recent years through promotional disputes and long spells of inactivity.
Previously predicted as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter ready to be aggressive in a tentative early stages.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who operated with a tight guard to narrowly win the cleaner periods.
The audience's tolerance decreased during constant clinching, with Parker going down multiple occasions during clinches.
The underdog closed well, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - working with Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Hatton Memorial Inspires Local Rivalry Battle
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent Manchester vs Manchester contest to win the continental title.
The venue fell silent for a deeply poignant memorial before the fight as ten bells sounded in remembrance of the city's native Hatton, who died at age 46 in last month.
It was the premier televised fight night in the urban center since the passing of Hatton. As the concluding sound ended, the silence became a chant of "only one Hatton".
The competition inside the ropes reflected the feeling. Arthur was sent to the canvas by a significant blow squarely on the jaw in the early round, getting up unsteadily to his feet on the count of eight.
But the red-colored equipment of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was marked up early, significant bruising forming under his eye as the duo traded punishing blows.
Rea, 27, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
Arthur barely secured the result with judges scorecards of 114-114, 115-113 and wider gap, but the two athletes were persistent and courageous, all the qualities their inspiration Hatton represented.
