UK light heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a match where the techniques failed to mesh, with frequent clinching marring the action.
The officials had it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi stated in the arena as he was met by boos from the crowd.
The British fighter got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Various analysts felt Parker, thirty-one, should have been awarded the decision but the contender endured the second defeat of his 28-bout professional journey.
Buatsi Earns Win in Dull Match
Buatsi's progress has slowed in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what appears to be a last chance - under recent support.
He opened tentatively, with both competitors prepared to take risks in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to narrowly win the better periods.
The crowd's patience decreased because of regular grabbing, with Parker slipping to the canvas several times during grappling.
Parker finished the stronger, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Battle
In the co-main event, Arthur beat Bradley Rea by close verdict in a excellent local rivalry battle to secure the continental championship.
The arena fell silent for a extremely emotional homage ahead of the contest as a bell ceremony rang in honor of the city's native Ricky Hatton, who died at age 46 in recently.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the final chime ended, the silence transitioned to a roar of "there's just one Hatton".
The action within the ring reflected the feeling. Arthur was knocked down by a powerful punch directly to the face in the early round, rising shakily to his position on the referee's count.
But the red-colored equipment of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was damaged soon, heavy swelling appearing under his face as the pair traded punishing blows.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the result with official scores of draw, narrow lead and 115-112, but the two athletes were persistent and brave, all the qualities their idol the legend embodied.
