UK light heavyweight Joshua Buatsi earned a win yet disappointing start to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive 10-round bout at the Manchester venue.
But Parker found success, delivering effective individual punches in a fight where the styles failed to mesh, with excessive holding spoiling the fight.
Two judges had it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They win," Buatsi said in the ringside as he was greeted with boos from the audience.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a 20th career victory.
Several boxing experts thought the challenger, thirty-one, merited the decision but the British boxer suffered the second defeat of his 28-bout career.
Buatsi Earns Win in Slow Encounter
Buatsi's progress has plateaued in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of UK boxing, he now is positioned trying to achieve expectations - possibly in what seems like a last chance - under fresh management.
He opened tentatively, with both competitors prepared to take risks in a tentative early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for Buatsi, who utilized a solid defense to barely take the better rounds.
The crowd's patience wore thin during frequent holding, with the challenger going down several times during grappling.
The underdog finished the stronger, but multiple periods were challenging to assess. However, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor advances, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Hatton Tribute Fuels Manchester Derby Fight
In the supporting bout, Arthur beat Bradley Rea by divided decision in a outstanding all-Manchester battle to win the European light heavyweight belt.
The venue became quiet for a extremely emotional memorial ahead of the contest as a bell ceremony tolled in honor of the city's native Hatton, who succumbed 46 years old in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the final chime ended, the stillness gave way to a roar of "only one Ricky Hatton".
The action during the bout matched the sentiment. The eventual winner was floored by a significant blow squarely on the chin in the second round, rising shakily to his feet on the referee's count.
But the red-colored shorts of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was marked up early, noticeable damage developing under his orbital area as the duo traded punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with stinging uppercuts as the intensity seldom decreased over 12 rounds.
The victor narrowly won the decision with scoring tallies of even score, close margin and clearer margin, but the two athletes were persistent and courageous, everything their hero the legend embodied.
