British light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But Parker had his moments, landing some telling single shots in a match where the techniques failed to mesh, with excessive holding marring the action.
The scoring judges scored it 96-94 for to the winner, with the third a 95-95.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the arena as he was greeted with disapproval from the spectators.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to earn a 20th pro success.
Various analysts felt Parker, 31, deserved the win but the British boxer experienced the second loss of his 28-bout professional journey.
Buatsi Claims Triumph in Dull Affair
The fighter's advancement has plateaued in recent times through management issues and considerable time of inactivity.
Once tipped as the future of British boxing, he now is positioned trying to realize his potential - maybe in what feels like a last chance - under fresh management.
He started carefully, with both competitors ready to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was making just his second bout at light heavyweight.
By the middle rounds, the underdog had made it competitive, causing problems for Buatsi, who utilized a protective stance to edge the cleaner stanzas.
The audience's tolerance diminished because of frequent holding, with Parker falling to the floor multiple occasions during clinches.
The underdog finished the stronger, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a excellent Manchester vs Manchester fight to capture the European light-heavyweight title.
The arena became quiet for a extremely emotional homage prior to the bout as a bell ceremony sounded in honor of Manchester's own Ricky Hatton, who died at age 46 in last month.
It was the initial significant broadcast match card in the location since Hatton's death. As the concluding sound ended, the stillness transitioned to a shout of "only one Ricky Hatton".
The fighting inside the ropes matched the emotion. Arthur was knocked down by a significant blow directly to the jaw in the early round, standing uncertainly to his position on the referee's count.
But the Manchester United-red attire of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was marked up quickly, noticeable damage developing under his orbital area as the pair exchanged punishing blows.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the result with scoring tallies of draw, close margin and wider gap, but both fighters were persistent and courageous, exactly what their idol the legend stood for.
