UK light-heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to his career under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a close ten-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful individual punches in a contest where the techniques never quite clicked, with frequent clinching spoiling the fight.
The scoring judges judged it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They succeed," the victor said in the arena as he was faced boos from the crowd.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts believed Parker, thirty-one, merited the win but the contender endured the second defeat of his 28-bout career.
The Champion Secures Win in Dull Match
His career development has slowed in the past few years through management issues and extended periods of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors prepared to take risks in a tentative initial rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who utilized a protective stance to narrowly win the more effective stanzas.
The crowd's patience wore thin during regular grabbing, with Parker going down several times during close exchanges.
Parker finished the stronger, but multiple periods were hard to judge. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of hard hitter Benavidez, and Russian star Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Hatton Tribute Fuels Manchester Derby Fight
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a excellent Manchester vs Manchester fight to secure the European light-heavyweight title.
The stadium fell silent for a extremely emotional homage prior to the bout as 10 bells tolled in honor of local hero Hatton, who passed away aged 46 in September.
It was the initial significant broadcast match card in the location since Hatton's death. As the concluding sound faded, the stillness gave way to a roar of "there's just one Ricky Hatton".
The fighting inside the ropes matched the sentiment. Arthur was floored by a powerful punch flush on the face in the early round, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was injured quickly, heavy swelling forming under his orbital area as the fighters traded hard punches.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the pace seldom decreased over the full distance.
The victor narrowly won the decision with judges scorecards of draw, 115-113 and clearer margin, but each competitor were persistent and brave, all the qualities their hero the legend embodied.
