UK light-heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a tight ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful clean blows in a fight where the styles didn't complement each other, with constant grabbing spoiling the action.
The scoring judges judged it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi said in the ringside as he was faced negative reactions from the audience.
The British fighter bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers thought the challenger, thirty-one, merited the decision but the contender experienced the second setback of his 28-match professional journey.
Buatsi Claims Win in Uneventful Match
His career development has plateaued in recent times through contract problems and extended periods of inactivity.
Previously predicted as the next star of UK boxing, he now is positioned trying to realize his potential - possibly in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors prepared to be aggressive in a calculated opening few rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after damaging his hand during the bout, was participating in his second bout at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a solid defense to narrowly win the better stanzas.
The audience's tolerance wore thin during constant clinching, with Parker falling to the floor multiple occasions during close exchanges.
Parker ended stronger, but multiple periods were hard to judge. However, ex-champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian star Bivol ruling the division, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Homage Inspires Manchester Derby Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by close verdict in a excellent Manchester vs Manchester battle to win the European light-heavyweight championship.
The arena fell silent for a deeply poignant homage ahead of the contest as ten bells tolled in remembrance of the city's native Hatton, who succumbed 46 years old in September.
It was the first major televised fight night in the urban center since Hatton's death. As the concluding sound ended, the stillness transitioned to a roar of "only one Ricky Hatton".
The action within the ring equaled the feeling. The eventual winner was sent to the canvas by a powerful punch squarely on the face in the early round, rising shakily to his footing on the count of eight.
But the red-colored shorts of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was injured soon, heavy swelling appearing under his orbital area as the pair landed punishing blows.
Rea, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with stinging uppercuts as the action seldom decreased over twelve rounds.
Arthur barely secured the result with scoring tallies of even score, 115-113 and wider gap, but each competitor were determined and full of heart, everything their hero the legend embodied.
