British light-heavyweight Joshua Buatsi secured a victory yet unimpressive start to life under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a competitive ten-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a match where the approaches never quite clicked, with constant grabbing spoiling the action.
The officials had it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi commented in the arena as he was greeted with disapproval from the spectators.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers believed the challenger, 31, deserved the decision but the contender endured the second loss of his 28-bout professional journey.
Buatsi Earns Win in Slow Match
His career development has plateaued in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was competing in only his second fight at the higher weight class.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a tight guard to edge the better periods.
The audience's tolerance decreased because of regular grabbing, with the challenger slipping to the canvas several times during grappling.
The underdog finished the stronger, but many rounds were difficult to score. However, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Hatton Homage Fuels Local Rivalry Fight
In the supporting bout, Arthur beat Rea by divided decision in a outstanding local rivalry fight to secure the European light heavyweight championship.
The venue fell silent for a profoundly moving memorial ahead of the contest as ten bells rang in honor of Manchester's own Hatton, who died 46 years old in September.
It was the first major televised boxing event in the urban center since Hatton's death. As the last bell ended, the silence became a chant of "there's just one Ricky Hatton".
The competition inside the ropes matched the feeling. Arthur was floored by a significant blow directly to the chin in the second round, rising shakily to his feet on the eight count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged early, heavy swelling forming under his orbital area as the fighters exchanged punishing blows.
Rea, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over 12 rounds.
Arthur narrowly won the decision with scoring tallies of even score, close margin and clearer margin, but both fighters were persistent and brave, exactly what their hero Hatton embodied.
