British light heavyweight Joshua Buatsi earned a win yet disappointing debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's punch output likely gained him a split decision in a tight 10-round contest at the boxing arena.
But Parker landed significant shots, landing some telling single shots in a fight where the techniques never quite clicked, with excessive holding disrupting the action.
The scoring judges had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best performance but what defines champions? They prevail," Buatsi stated in the ringside as he was met by negative reactions from the crowd.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in February - to secure a 20th pro success.
Several boxing experts felt the challenger, thirty-one, merited the win but the Derbyshire fighter suffered the second setback of his 28-fight career.
The Champion Claims Triumph in Dull Match
His career development has slowed in the past few years through management issues and considerable time of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to realize his potential - perhaps in what feels like a final roll of the dice - under recent support.
He opened tentatively, with the two boxers willing to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second bout at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to narrowly win the more effective periods.
The crowd's patience diminished during constant clinching, with Parker slipping to the canvas various instances during close exchanges.
The underdog finished the stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just one round.
Buatsi moves on, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates Manchester Derby Battle
In the co-main event, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry battle to capture the continental title.
The venue grew hushed for a extremely emotional memorial ahead of the contest as ten bells sounded in memory of the city's native Hatton, who succumbed at age 46 in September.
It was the first major televised fight night in the city since the passing of Hatton. As the concluding sound disappeared, the quiet gave way to a shout of "only one Hatton".
The competition within the ring matched the emotion. Arthur was floored by a significant blow squarely on the face in the early round, getting up unsteadily to his position on the eight count.
But the red-colored equipment of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was injured early, significant bruising forming under his orbital area as the fighters exchanged punishing blows.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with stinging uppercuts as the intensity seldom decreased over 12 rounds.
The victor edged the result with official scores of even score, close margin and clearer margin, but each competitor were persistent and brave, everything their idol the legend represented.
