British light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's punch output likely gained him a split decision in a tight 10-round bout at the Manchester venue.
But the challenger landed significant shots, delivering effective individual punches in a fight where the styles failed to mesh, with excessive holding spoiling the action.
Two judges judged it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my finest display but what do champions do? They succeed," the victor commented in the arena as he was met by disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, deserved the victory but the Derbyshire fighter suffered the second setback of his 28-bout professional journey.
The Champion Claims Triumph in Slow Encounter
The fighter's advancement has plateaued in the past few years through promotional disputes and extended periods of inactivity.
Once tipped as the next star of the British fight scene, he now finds himself trying to achieve expectations - maybe in what appears to be a last chance - under recent support.
He opened tentatively, with the two boxers willing to take risks in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second bout at the higher weight class.
By the middle rounds, the underdog had stayed in contention, making life awkward for the favorite, who utilized a solid defense to barely take the better periods.
The audience's tolerance wore thin amid frequent holding, with the challenger slipping to the canvas various instances during clinches.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian champion Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Inspires Local Rivalry Contest
In the secondary fight, Arthur defeated Rea by split-decision in a outstanding all-Manchester battle to secure the European light heavyweight title.
The stadium became quiet for a profoundly moving memorial ahead of the contest as 10 bells sounded in memory of the city's native Ricky Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast match card in the location since Hatton's death. As the concluding sound ended, the quiet transitioned to a chant of "there's just one Hatton".
The competition within the ring reflected the sentiment. Arthur was knocked down by a left hook flush on the jaw in the initial stage, rising shakily to his footing on the count of eight.
But the traditional red equipment of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up quickly, heavy swelling forming under his face as the pair landed powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over twelve rounds.
The victor edged the result with official scores of even score, narrow lead and clearer margin, but both fighters were persistent and full of heart, all the qualities their hero Hatton represented.
