British light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a tight ten-round contest at the boxing arena.
But the challenger found success, landing some telling clean blows in a match where the approaches failed to mesh, with constant grabbing marring the action.
Two judges scored it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my greatest performance but what defines champions? They succeed," the victor commented in the arena as he was greeted with negative reactions from the crowd.
The Londoner got back to winning after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts believed the challenger, 31, merited the victory but the contender endured the second defeat of his 28-fight career.
Buatsi Claims Triumph in Uneventful Match
Buatsi's progress has plateaued in recent times through management issues and extended periods of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to achieve expectations - maybe in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with the two boxers ready to be aggressive in a tentative initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a tight guard to narrowly win the cleaner rounds.
The audience's tolerance diminished because of regular grabbing, with Parker going down several times during close exchanges.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just one round.
Buatsi progresses, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Hatton Tribute Inspires Manchester Derby Contest
In the supporting bout, Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester contest to secure the continental belt.
The venue grew hushed for a deeply poignant homage ahead of the contest as 10 bells rang in remembrance of local hero Hatton, who died 46 years old in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the last bell faded, the quiet became a shout of "only one Hatton".
The competition inside the ropes reflected the feeling. Arthur was knocked down by a powerful punch directly to the face in the second round, rising shakily to his feet on the referee's count.
But the Manchester United-red equipment of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was damaged quickly, significant bruising developing under his face as the duo landed hard punches.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over the full distance.
Arthur edged the result with official scores of even score, close margin and 115-112, but both fighters were persistent and courageous, all the qualities their idol the legend stood for.
