British light heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a majority decision in a close 10-round fight at the Co-op Live Arena.
But Parker found success, landing some telling individual punches in a contest where the approaches never quite clicked, with frequent clinching spoiling the action.
Two judges had it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my best showing but what do champions do? They win," Buatsi said in the ringside as he was faced disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Various analysts felt the challenger, thirty-one, deserved the win but the British boxer suffered the second setback of his 28-match career.
The Champion Earns Victory in Dull Match
Buatsi's progress has plateaued in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter ready to be aggressive in a tentative early stages.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after damaging his hand mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for Buatsi, who utilized a protective stance to barely take the better rounds.
The spectators' acceptance decreased because of regular grabbing, with the challenger going down various instances during clinches.
The underdog ended stronger, but several stanzas were challenging to assess. However, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - on this evidence - still looks steep.
Hatton Memorial Motivates Manchester Derby Battle
In the secondary fight, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific all-Manchester contest to secure the continental title.
The arena fell silent for a extremely emotional memorial before the fight as ten bells sounded in honor of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the final chime disappeared, the stillness gave way to a roar of "only one Hatton".
The action within the ring reflected the feeling. The eventual winner was sent to the canvas by a left hook directly to the face in the initial stage, getting up unsteadily to his position on the referee's count.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was injured early, noticeable damage forming under his orbital area as the pair traded punishing blows.
Rea, 27, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
The victor edged the result with scoring tallies of draw, close margin and wider gap, but the two athletes were determined and full of heart, everything their hero Hatton embodied.
