UK light heavyweight Joshua Buatsi secured a victory yet disappointing start to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful single shots in a contest where the approaches didn't complement each other, with constant grabbing marring the contest.
The scoring judges had it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my best performance but what do champions do? They succeed," the victor stated in the ringside as he was greeted with boos from the audience.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Several boxing experts believed Parker, 31, deserved the victory but the contender experienced the second defeat of his 28-bout career.
The Champion Secures Win in Slow Encounter
His career development has plateaued in the past few years through promotional disputes and extended periods of lack of fights.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - possibly in what appears to be a last chance - under recent support.
He opened tentatively, with neither fighter ready to take risks in a tentative initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, Parker had kept it close, causing problems for the favorite, who utilized a protective stance to narrowly win the cleaner rounds.
The spectators' acceptance diminished because of constant clinching, with Parker falling to the floor several times during grappling.
The underdog closed well, but many rounds were hard to judge. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent local rivalry contest to capture the European light heavyweight championship.
The venue grew hushed for a profoundly moving homage before the fight as ten bells rang in memory of local hero Hatton, who passed away aged 46 in September.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound faded, the silence gave way to a shout of "there's only one Ricky Hatton".
The fighting during the bout equaled the emotion. The eventual winner was sent to the canvas by a left hook squarely on the jaw in the second round, rising shakily to his feet on the referee's count.
But the red-colored shorts of the fighter soon pressed ahead again. Across the ring, Rea - in rival City blue - was damaged soon, significant bruising forming under his eye as the fighters traded powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity hardly diminished over 12 rounds.
Arthur barely secured the decision with scoring tallies of 114-114, narrow lead and clearer margin, but both fighters were relentless and brave, everything their idol the legend embodied.
