British light heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a close ten-round contest at the Manchester venue.
But the challenger landed significant shots, landing some telling clean blows in a fight where the styles failed to mesh, with constant grabbing spoiling the contest.
The officials scored it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my finest showing but what do champions do? They prevail," the victor commented in the ring as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to claim a 20th pro success.
Some ringside observers thought the challenger, 31, merited the decision but the British boxer suffered the second loss of his 28-fight professional journey.
The Champion Claims Triumph in Uneventful Encounter
The fighter's advancement has plateaued in recent times through contract problems and extended periods of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a last chance - under fresh management.
He opened tentatively, with neither fighter prepared to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second bout at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a solid defense to narrowly win the cleaner rounds.
The crowd's patience diminished amid frequent holding, with Parker slipping to the canvas several times during grappling.
The underdog ended stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the presence of heavy hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Hatton Tribute Inspires Local Rivalry Contest
In the co-main event, Arthur overcame Rea by divided decision in a terrific all-Manchester fight to secure the European light heavyweight title.
The venue grew hushed for a deeply poignant homage before the fight as ten bells tolled in memory of local hero Ricky Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the location since Hatton's death. As the final chime faded, the quiet became a chant of "there's just one Ricky Hatton".
The fighting during the bout reflected the feeling. Arthur was knocked down by a significant blow directly to the jaw in the second round, rising shakily to his footing on the count of eight.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was damaged soon, significant bruising appearing under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the pace rarely dropped over the full distance.
Arthur narrowly won the decision with official scores of 114-114, close margin and wider gap, but both fighters were relentless and full of heart, exactly what their idol Hatton stood for.
