UK light heavyweight Joshua Buatsi made a winning yet underwhelming start to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a tight ten-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a fight where the approaches didn't complement each other, with excessive holding disrupting the action.
The officials judged it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi said in the ring as he was greeted with boos from the audience.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, should have been awarded the decision but the British boxer suffered the second loss of his 28-fight professional journey.
The Champion Secures Triumph in Dull Match
The fighter's advancement has plateaued in the past few years through promotional disputes and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors prepared to overcommit in a calculated initial rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to narrowly win the more effective stanzas.
The crowd's patience diminished during frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Hatton Homage Fuels All-Manchester Battle
In the secondary fight, Arthur beat Rea by split-decision in a outstanding Manchester vs Manchester battle to win the continental championship.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as 10 bells rang in memory of Manchester's own Hatton, who succumbed aged 46 in September.
It was the first major televised match card in the urban center since Hatton's passing. As the final chime ended, the stillness transitioned to a roar of "there's only one Hatton".
The competition inside the ropes reflected the feeling. Arthur was sent to the canvas by a powerful punch flush on the chin in the initial stage, standing uncertainly to his feet on the eight count.
But the traditional red attire of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up quickly, significant bruising developing under his orbital area as the pair exchanged punishing blows.
The challenger, 27, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the pace hardly diminished over 12 rounds.
The victor barely secured the verdict with scoring tallies of 114-114, 115-113 and 115-112, but the two athletes were relentless and full of heart, everything their idol Hatton stood for.
