UK light-heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a tight 10-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful single shots in a match where the techniques never quite clicked, with frequent clinching marring the fight.
The scoring judges scored it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They succeed," the victor stated in the ring as he was faced disapproval from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Some ringside observers believed the challenger, thirty-one, merited the victory but the Derbyshire fighter experienced the second setback of his 28-fight professional journey.
Buatsi Secures Victory in Dull Encounter
The fighter's advancement has plateaued in recent times through management issues and considerable time of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under recent support.
He started carefully, with the two boxers prepared to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after breaking his hand during the bout, was participating in his second fight at light-heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who operated with a solid defense to barely take the more effective rounds.
The audience's tolerance diminished amid constant clinching, with the challenger falling to the floor various instances during grappling.
Parker closed well, but multiple periods were challenging to assess. Although, ex-champion the boxing analyst - working with Dazn - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the road to world glory - based on this performance - still appears challenging.
Hatton Tribute Inspires Manchester Derby Battle
In the secondary fight, Lyndon Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester fight to win the European light heavyweight title.
The arena grew hushed for a profoundly moving tribute ahead of the contest as 10 bells rang in honor of Manchester's own Hatton, who passed away aged 46 in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the final chime faded, the stillness became a chant of "only one Hatton".
The competition within the ring matched the sentiment. The eventual winner was floored by a powerful punch directly to the chin in the second round, getting up unsteadily to his position on the eight count.
But the traditional red equipment of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was injured quickly, heavy swelling forming under his eye as the duo traded punishing blows.
Rea, 27, landed power punches but the champion, 34, fought fire with fire with powerful upward punches as the action rarely dropped over the full distance.
The victor edged the decision with official scores of 114-114, narrow lead and 115-112, but the two athletes were relentless and full of heart, everything their idol the legend stood for.
