UK light heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a tight 10-round fight at the Co-op Live Arena.
But Parker had his moments, landing some telling individual punches in a fight where the approaches didn't complement each other, with frequent clinching marring the action.
The scoring judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor stated in the arena as he was greeted with boos from the crowd.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts thought the challenger, 31, deserved the victory but the contender endured the second defeat of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Match
The fighter's advancement has slowed in recent years through contract problems and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to fulfil that early promise - possibly in what appears to be a last chance - under recent support.
He began cautiously, with neither fighter prepared to be aggressive in a tentative early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second bout at the higher weight class.
By the fight's midpoint, Parker had kept it close, making life awkward for Buatsi, who utilized a protective stance to barely take the more effective periods.
The audience's tolerance decreased because of regular grabbing, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the secondary fight, Arthur overcame Rea by close verdict in a terrific local rivalry fight to win the European light heavyweight championship.
The arena fell silent for a extremely emotional homage prior to the bout as a bell ceremony tolled in remembrance of Manchester's own Ricky Hatton, who died at age 46 in recently.
It was the first major televised match card in the city since Hatton's death. As the last bell faded, the stillness became a roar of "there's only one Ricky Hatton".
The fighting within the ring equaled the sentiment. Arthur was knocked down by a powerful punch flush on the jaw in the early round, standing uncertainly to his position on the count of eight.
But the red-colored attire of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was marked up soon, heavy swelling developing under his face as the pair traded powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the action hardly diminished over the full distance.
Arthur edged the verdict with judges scorecards of even score, 115-113 and 115-112, but each competitor were persistent and courageous, exactly what their idol Hatton stood for.
