British light heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to life under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful clean blows in a contest where the approaches didn't complement each other, with constant grabbing disrupting the contest.
Two judges had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best display but what do champions do? They win," Buatsi stated in the ring as he was greeted with disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers believed Parker, 31, should have been awarded the victory but the Derbyshire fighter experienced the second defeat of his 28-bout professional journey.
The Champion Earns Win in Slow Match
Buatsi's progress has stalled in recent years through contract problems and long spells of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under recent support.
He began cautiously, with neither fighter ready to take risks in a calculated initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who worked behind a tight guard to narrowly win the cleaner stanzas.
The spectators' acceptance diminished during regular grabbing, with Parker slipping to the canvas multiple occasions during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
The victor moves on, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to secure the continental belt.
The venue fell silent for a deeply poignant homage before the fight as 10 bells tolled in honor of the city's native Ricky Hatton, who succumbed 46 years old in September.
It was the initial significant broadcast fight night in the urban center since Hatton's passing. As the final chime faded, the quiet became a roar of "there's only one Hatton".
The action within the ring equaled the feeling. The eventual winner was floored by a powerful punch flush on the jaw in the second round, standing uncertainly to his position on the referee's count.
But the traditional red attire of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was injured quickly, noticeable damage forming under his face as the fighters exchanged powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the intensity seldom decreased over twelve rounds.
Arthur edged the result with scoring tallies of even score, close margin and 115-112, but the two athletes were determined and full of heart, exactly what their inspiration Hatton stood for.
