British light heavyweight Joshua Buatsi made a winning yet unimpressive debut to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight ten-round fight at the boxing arena.
But the challenger had his moments, delivering effective individual punches in a fight where the styles didn't complement each other, with constant grabbing marring the action.
The scoring judges scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best display but what do champions do? They prevail," Buatsi commented in the ring as he was faced boos from the crowd.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Some ringside observers felt the challenger, thirty-one, deserved the victory but the British boxer experienced the second loss of his 28-bout professional journey.
The Champion Claims Victory in Dull Match
Buatsi's progress has slowed in recent years through management issues and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now finds himself trying to achieve expectations - maybe in what seems like a last chance - under fresh management.
He opened tentatively, with the two boxers ready to take risks in a cagey early stages.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand mid-fight, was making just his second bout at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who utilized a protective stance to narrowly win the cleaner rounds.
The audience's tolerance wore thin during constant clinching, with Parker slipping to the canvas multiple occasions during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just only one stanza.
The victor moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Motivates Manchester Derby Battle
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a outstanding all-Manchester fight to win the European light-heavyweight championship.
The stadium grew hushed for a deeply poignant memorial ahead of the contest as ten bells sounded in memory of local hero Hatton, who passed away at age 46 in last month.
It was the first major televised boxing event in the city since Hatton's passing. As the last bell faded, the silence became a chant of "there's just one Hatton".
The fighting within the ring reflected the sentiment. The eventual winner was knocked down by a significant blow directly to the chin in the second round, rising shakily to his feet on the count of eight.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in rival City blue - was damaged soon, heavy swelling developing under his face as the fighters landed powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
The victor barely secured the verdict with judges scorecards of 114-114, 115-113 and clearer margin, but both fighters were determined and courageous, everything their hero the legend embodied.
