British light-heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a majority decision in a tight ten-round bout at the Manchester venue.
But Parker found success, delivering effective clean blows in a fight where the techniques didn't complement each other, with constant grabbing marring the action.
The officials scored it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my finest showing but how do champions respond? They win," the victor commented in the ringside as he was greeted with negative reactions from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in February - to earn a 20th pro success.
Some ringside observers thought the challenger, thirty-one, merited the decision but the British boxer experienced the second loss of his 28-match career.
Buatsi Earns Victory in Uneventful Encounter
His career development has plateaued in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of British boxing, he now stands trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He opened tentatively, with the two boxers willing to be aggressive in a calculated early stages.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second fight at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a tight guard to barely take the more effective rounds.
The spectators' acceptance wore thin because of frequent holding, with the challenger slipping to the canvas various instances during close exchanges.
Parker ended stronger, but many rounds were challenging to assess. Although, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Lyndon Arthur defeated Bradley Rea by divided decision in a outstanding local rivalry fight to win the European light-heavyweight belt.
The arena grew hushed for a profoundly moving tribute prior to the bout as ten bells sounded in honor of the city's native Ricky Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a shout of "only one Ricky Hatton".
The fighting within the ring reflected the sentiment. Arthur was sent to the canvas by a powerful punch flush on the face in the initial stage, rising shakily to his footing on the count of eight.
But the traditional red attire of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was marked up early, noticeable damage developing under his eye as the duo landed powerful shots.
Rea, 27, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the action rarely dropped over 12 rounds.
The victor narrowly won the decision with official scores of even score, narrow lead and clearer margin, but each competitor were relentless and brave, exactly what their idol the legend embodied.
