UK light-heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a close 10-round bout at the boxing arena.
But the challenger had his moments, connecting with powerful single shots in a match where the techniques didn't complement each other, with excessive holding disrupting the fight.
The scoring judges scored it 96-94 to the winner, with the third a even score.
"It wasn't my greatest display but how do champions respond? They succeed," the victor said in the ring as he was faced boos from the spectators.
The Londoner bounced back after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts thought the challenger, 31, deserved the decision but the contender suffered the second loss of his 28-match career.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has plateaued in recent times through contract problems and long spells of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with both competitors ready to take risks in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was making just his second appearance at light-heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to narrowly win the better rounds.
The crowd's patience wore thin because of frequent holding, with Parker slipping to the canvas several times during clinches.
Parker closed well, but several stanzas were difficult to score. Although, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, giving Buatsi just a single round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Hatton Tribute Inspires Manchester Derby Fight
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a outstanding all-Manchester fight to win the European light-heavyweight championship.
The arena became quiet for a profoundly moving homage ahead of the contest as 10 bells sounded in honor of local hero Ricky Hatton, who died aged 46 in September.
It was the first major televised boxing event in the city since Hatton's passing. As the last bell faded, the quiet gave way to a shout of "there's only one Ricky Hatton".
The competition inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a significant blow squarely on the chin in the early round, standing uncertainly to his feet on the count of eight.
But the traditional red equipment of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was injured quickly, significant bruising appearing under his orbital area as the fighters traded powerful shots.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur edged the result with judges scorecards of draw, close margin and 115-112, but both fighters were persistent and brave, all the qualities their hero Hatton embodied.
