UK light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a competitive ten-round fight at the Manchester venue.
But Parker landed significant shots, delivering effective individual punches in a fight where the techniques didn't complement each other, with constant grabbing marring the fight.
Two judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my greatest display but what do champions do? They win," Buatsi stated in the arena as he was met by negative reactions from the crowd.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers thought the challenger, thirty-one, deserved the win but the British boxer endured the second setback of his 28-bout career.
The Champion Earns Triumph in Uneventful Encounter
Buatsi's progress has slowed in the past few years through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He began cautiously, with both competitors ready to take risks in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second bout at light-heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who utilized a solid defense to barely take the more effective periods.
The spectators' acceptance wore thin during regular grabbing, with Parker going down several times during clinches.
The underdog ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Motivates All-Manchester Fight
In the co-main event, Arthur beat Rea by close verdict in a outstanding local rivalry battle to capture the European light-heavyweight belt.
The stadium fell silent for a profoundly moving homage before the fight as a bell ceremony tolled in remembrance of Manchester's own Ricky Hatton, who died 46 years old in September.
It was the premier televised fight night in the location since Hatton's passing. As the last bell faded, the stillness became a shout of "there's just one Ricky Hatton".
The action within the ring reflected the emotion. Arthur was sent to the canvas by a left hook directly to the jaw in the early round, rising shakily to his feet on the count of eight.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was damaged early, heavy swelling appearing under his face as the fighters traded hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the action seldom decreased over 12 rounds.
Arthur barely secured the decision with official scores of draw, narrow lead and wider gap, but both fighters were determined and brave, exactly what their hero Hatton represented.
