British light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a majority decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful clean blows in a contest where the techniques never quite clicked, with excessive holding marring the action.
The officials judged it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my best display but what do champions do? They succeed," the victor commented in the ringside as he was greeted with boos from the crowd.
The Londoner bounced back after his maiden career setback - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Various analysts believed the challenger, 31, should have been awarded the win but the British boxer suffered the second defeat of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Encounter
The fighter's advancement has stalled in the past few years through contract problems and extended periods of lack of fights.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a last chance - under fresh management.
He started carefully, with both competitors ready to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who operated with a solid defense to narrowly win the better rounds.
The spectators' acceptance diminished because of constant clinching, with the challenger going down multiple occasions during clinches.
Parker ended stronger, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a terrific local rivalry contest to capture the continental title.
The arena grew hushed for a profoundly moving memorial ahead of the contest as a bell ceremony tolled in honor of the city's native Hatton, who succumbed 46 years old in last month.
It was the premier televised match card in the location since the passing of Hatton. As the concluding sound ended, the stillness transitioned to a shout of "there's only one Hatton".
The fighting inside the ropes reflected the emotion. Arthur was knocked down by a significant blow squarely on the jaw in the initial stage, rising shakily to his feet on the eight count.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, Rea - in rival City blue - was damaged quickly, significant bruising forming under his orbital area as the fighters exchanged hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
Arthur narrowly won the result with official scores of even score, close margin and 115-112, but the two athletes were relentless and full of heart, exactly what their hero Hatton represented.
