British light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a close ten-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective clean blows in a match where the styles failed to mesh, with excessive holding spoiling the fight.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest performance but what do champions do? They win," the victor stated in the ringside as he was met by disapproval from the spectators.
The British fighter returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers felt the challenger, 31, deserved the win but the British boxer suffered the second defeat of his 28-match professional journey.
The Champion Secures Victory in Uneventful Affair
His career development has slowed in recent times through management issues and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to achieve expectations - maybe in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with both competitors willing to be aggressive in a calculated 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 during the bout, was making just his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who utilized a protective stance to edge the cleaner stanzas.
The crowd's patience diminished during constant clinching, with Parker falling to the floor several times during clinches.
The underdog closed well, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - commentating on Dazn - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Motivates Local Rivalry Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a excellent Manchester vs Manchester contest to secure the European light-heavyweight championship.
The stadium fell silent for a extremely emotional memorial before the fight as a bell ceremony rang in remembrance of local hero Hatton, who succumbed at age 46 in September.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the stillness gave way to a roar of "only one Hatton".
The competition during the bout matched the sentiment. The eventual winner was knocked down by a significant blow flush on the face in the early round, standing uncertainly to his footing on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was damaged quickly, significant bruising appearing under his orbital area as the pair exchanged powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over twelve rounds.
The victor edged the decision with scoring tallies of draw, narrow lead and wider gap, but both fighters were persistent and courageous, everything their hero the legend stood for.
