UK light heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a tight 10-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a match where the techniques didn't complement each other, with excessive holding marring the contest.
The scoring judges judged it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi stated in the arena as he was met by negative reactions from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Several boxing experts thought Parker, 31, merited the victory but the Derbyshire fighter suffered the second defeat of his 28-match career.
Buatsi Earns Triumph in Uneventful Match
The fighter's advancement has plateaued in recent years through contract problems and extended periods of lack of fights.
Earlier forecast as the future of British boxing, he now stands trying to achieve expectations - possibly in what appears to be a last chance - under new promotional backing.
He started carefully, with neither fighter ready to be aggressive in a tentative early stages.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second bout at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the cleaner rounds.
The crowd's patience diminished during constant clinching, with Parker going down multiple occasions during grappling.
The underdog closed well, but multiple periods were challenging to assess. Although, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the supporting bout, Arthur defeated Rea by close verdict in a excellent local rivalry fight to secure the European light heavyweight belt.
The arena fell silent for a deeply poignant memorial before the fight as a bell ceremony sounded in honor of the city's native Hatton, who passed away at age 46 in recently.
It was the first major televised boxing event in the location since Hatton's passing. As the last bell faded, the silence gave way to a shout of "there's just one Ricky Hatton".
The fighting within the ring matched the sentiment. The eventual winner was sent to the canvas by a powerful punch squarely on the chin in the early round, rising shakily to his footing on the count of eight.
But the traditional red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged quickly, noticeable damage developing under his eye as the fighters traded powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the verdict with scoring tallies of draw, close margin and wider gap, but both fighters were determined and full of heart, exactly what their inspiration the legend stood for.
