British light-heavyweight Joshua Buatsi secured a victory yet disappointing start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a competitive ten-round bout at the Manchester venue.
But the challenger found success, delivering effective single shots in a contest where the styles didn't complement each other, with excessive holding spoiling the fight.
The officials had it 96-94 for to the winner, with the final judge a even score.
"It wasn't my greatest performance but what do champions do? They succeed," the victor commented in the ring as he was met by disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th pro success.
Some ringside observers thought Parker, thirty-one, merited the win but the contender experienced the second loss of his 28-match career.
The Champion Earns Win in Slow Match
The fighter's advancement has stalled in recent years through promotional disputes and long spells of lack of fights.
Earlier forecast as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He started carefully, with the two boxers willing to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second bout at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who operated with a solid defense to narrowly win the more effective periods.
The crowd's patience decreased because of regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. However, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Tribute Motivates All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to win the continental belt.
The venue fell silent for a profoundly moving homage before the fight as a bell ceremony sounded in remembrance of local hero Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the location since Hatton's passing. As the concluding sound faded, the quiet became a shout of "there's only one Ricky Hatton".
The action inside the ropes equaled the emotion. The eventual winner was floored by a powerful punch squarely on the face in the second round, getting up unsteadily to his footing on the referee's count.
But the traditional red attire of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was marked up soon, noticeable damage developing under his face as the fighters landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with stinging uppercuts as the action seldom decreased over the full distance.
Arthur barely secured the verdict with official scores of 114-114, close margin and wider gap, but the two athletes were determined and full of heart, everything their idol Hatton embodied.
