British light heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a close ten-round fight at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a match where the techniques didn't complement each other, with constant grabbing marring the contest.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest performance but what defines champions? They prevail," the victor said in the arena as he was faced boos from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Various analysts believed the challenger, thirty-one, merited the decision but the Derbyshire fighter endured the second setback of his 28-bout career.
The Champion Secures Win in Dull Match
The fighter's advancement has slowed in the past few years through contract problems and extended periods of lack of fights.
Previously predicted as the future of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter prepared to be aggressive in a tentative opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for the favorite, who worked behind a tight guard to narrowly win the more effective stanzas.
The audience's tolerance wore thin because of frequent holding, with the challenger going down various instances during close exchanges.
Parker closed well, but many rounds were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Arthur overcame Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to win the continental belt.
The arena grew hushed for a deeply poignant tribute ahead of the contest as ten bells tolled in honor of local hero Hatton, who died 46 years old in last month.
It was the first major televised boxing event in the urban center since Hatton's passing. As the last bell faded, the quiet became a chant of "there's only one Hatton".
The competition within the ring equaled the emotion. Arthur was sent to the canvas by a left hook flush on the jaw in the initial stage, standing uncertainly to his position on the count of eight.
But the traditional red shorts of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up early, significant bruising appearing under his face as the fighters traded powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, responded in kind with powerful upward punches as the intensity rarely dropped over 12 rounds.
The victor edged the verdict with judges scorecards of 114-114, close margin and clearer margin, but both fighters were relentless and brave, all the qualities their inspiration the legend embodied.
