British light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a close ten-round fight at the Co-op Live Arena.
But Parker found success, landing some telling individual punches in a contest where the approaches never quite clicked, with excessive holding marring the fight.
The officials scored it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They succeed," Buatsi stated in the ringside as he was met by negative reactions from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers thought the challenger, 31, merited the win but the British boxer suffered the second defeat of his 28-fight professional journey.
Buatsi Earns Triumph in Slow Encounter
His career development has stalled in recent years through contract problems and considerable time of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with neither fighter prepared to be aggressive in a cagey initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was making just his second fight at the higher weight class.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who operated with a solid defense to barely take the better stanzas.
The spectators' acceptance diminished amid frequent holding, with Parker going down various instances during close exchanges.
The underdog ended stronger, but several stanzas were difficult to score. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor progresses, but with the likes of power puncher Benavidez, and Russian champion Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Arthur overcame Bradley Rea by split-decision in a excellent Manchester vs Manchester contest to secure the European light heavyweight championship.
The venue became quiet for a deeply poignant homage prior to the bout as ten bells tolled in memory of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the urban center since Hatton's passing. As the concluding sound ended, the quiet transitioned to a shout of "there's only one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was floored by a powerful punch squarely on the face in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up quickly, heavy swelling developing under his eye as the duo landed punishing blows.
The challenger, 27, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over the full distance.
The victor narrowly won the verdict with official scores of even score, 115-113 and wider gap, but each competitor were relentless and courageous, all the qualities their inspiration the legend stood for.
