British light heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a close 10-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a fight where the techniques failed to mesh, with excessive holding marring the fight.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi commented in the ringside as he was met by negative reactions from the audience.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th pro success.
Some ringside observers felt Parker, thirty-one, deserved the victory but the contender suffered the second setback of his 28-fight career.
Buatsi Secures Victory in Dull Match
Buatsi's progress has plateaued in the past few years through management issues and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors ready to take risks in a tentative initial rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to edge the cleaner periods.
The audience's tolerance wore thin during constant clinching, with the challenger going down various instances during grappling.
Parker finished the stronger, but many rounds were hard to judge. However, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to win the European light heavyweight championship.
The arena fell silent for a profoundly moving homage prior to the bout as 10 bells tolled in memory of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised match card in the urban center since Hatton's death. As the concluding sound disappeared, the stillness gave way to a shout of "there's just one Ricky Hatton".
The action inside the ropes equaled the feeling. Arthur was sent to the canvas by a powerful punch squarely on the jaw in the early round, getting up unsteadily to his footing on the eight count.
But the traditional red attire of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was injured quickly, significant bruising developing under his face as the duo landed powerful shots.
Rea, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the verdict with scoring tallies of draw, 115-113 and clearer margin, but the two athletes were relentless and courageous, everything their hero the legend stood for.
