UK light heavyweight Joshua Buatsi secured a victory yet disappointing debut to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive ten-round bout at the boxing arena.
But Parker landed significant shots, landing some telling single shots in a contest where the techniques didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my finest showing but how do champions respond? They win," the victor said in the arena as he was met by disapproval from the spectators.
The Londoner got back to winning after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, should have been awarded the win but the British boxer suffered the second loss of his 28-bout professional journey.
Buatsi Claims Victory in Dull Affair
The fighter's advancement has stalled in the past few years through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now stands trying to realize his potential - maybe in what feels like a last chance - under new promotional backing.
He started carefully, with both competitors willing to overcommit in a tentative opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second fight at light heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for the favorite, who utilized a solid defense to barely take the cleaner stanzas.
The audience's tolerance diminished because of frequent holding, with the challenger falling to the floor multiple occasions during clinches.
Parker finished the stronger, but multiple periods were challenging to assess. However, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Fuels Local Rivalry Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific all-Manchester contest to secure the continental title.
The venue grew hushed for a profoundly moving memorial before the fight as a bell ceremony sounded in memory of the city's native Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the urban center since Hatton's death. As the concluding sound ended, the stillness gave way to a roar of "there's only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was sent to the canvas by a significant blow directly to the jaw in the initial stage, rising shakily to his feet on the eight count.
But the red-colored shorts of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was injured early, noticeable damage forming under his face as the duo landed hard punches.
Rea, 27, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur narrowly won the verdict with official scores of draw, close margin and clearer margin, but the two athletes were determined and courageous, all the qualities their inspiration the legend stood for.
