British light heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a majority decision in a close 10-round contest at the boxing arena.
But Parker landed significant shots, connecting with powerful single shots in a contest where the styles didn't complement each other, with excessive holding spoiling the contest.
Two judges had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what do champions do? They succeed," Buatsi stated in the ring as he was greeted with disapproval from the audience.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts believed Parker, thirty-one, deserved the win but the Derbyshire fighter endured the second setback of his 28-fight career.
Buatsi Claims Triumph in Slow Encounter
His career development has stalled in recent years through management issues and extended periods of lack of fights.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to realize his potential - maybe in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to overcommit in a tentative early stages.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, making life awkward for the favorite, who worked behind a tight guard to narrowly win the more effective rounds.
The crowd's patience diminished amid constant clinching, with the challenger falling to the floor several times during clinches.
The underdog closed well, but several stanzas were challenging to assess. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian champion Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Motivates Manchester Derby Fight
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a outstanding all-Manchester fight to capture the European light heavyweight belt.
The arena fell silent for a extremely emotional tribute before the fight as ten bells rang in remembrance of the city's native Ricky Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the city since Hatton's death. As the last bell ended, the stillness became a chant of "only one Ricky Hatton".
The competition during the bout matched the sentiment. Arthur was knocked down by a significant blow flush on the chin in the early round, rising shakily to his position on the referee's count.
But the red-colored equipment of Arthur soon advanced again. Across the ring, Rea - in rival City blue - was injured quickly, heavy swelling developing under his face as the duo exchanged punishing blows.
Rea, 27, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the action hardly diminished over twelve rounds.
The victor narrowly won the decision with judges scorecards of draw, narrow lead and clearer margin, but the two athletes were persistent and full of heart, exactly what their hero Hatton represented.
