UK light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But the challenger found success, connecting with powerful single shots in a fight where the approaches never quite clicked, with excessive holding marring the fight.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi said in the ringside as he was greeted with disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts believed the challenger, 31, should have been awarded the win but the British boxer endured the second loss of his 28-bout professional journey.
Buatsi Secures Win in Slow Affair
The fighter's advancement has slowed in recent times through promotional disputes and long spells of inactivity.
Once tipped as the next star of UK boxing, he now stands trying to achieve expectations - maybe in what seems like a last chance - under recent support.
He began cautiously, with both competitors ready to be aggressive in a tentative opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a tight guard to edge the better periods.
The spectators' acceptance decreased amid constant clinching, with the challenger slipping to the canvas multiple occasions during close exchanges.
Parker finished the stronger, but several stanzas were hard to judge. Nevertheless, ex-champion Carl Frampton - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Arthur beat Rea by close verdict in a excellent local rivalry battle to secure the continental belt.
The arena became quiet for a profoundly moving tribute ahead of the contest as a bell ceremony sounded in honor of Manchester's own Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the concluding sound ended, the silence transitioned to a chant of "there's just one Hatton".
The fighting inside the ropes matched the sentiment. The eventual winner was knocked down by a powerful punch squarely on the chin in the second round, standing uncertainly to his position on the eight count.
But the traditional red attire of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was damaged early, significant bruising appearing under his eye as the pair traded powerful shots.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with stinging uppercuts as the action hardly diminished over the full distance.
Arthur barely secured the result with official scores of 114-114, close margin and clearer margin, but each competitor were relentless and brave, exactly what their hero the legend stood for.
