UK light-heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a close 10-round fight at the boxing arena.
But Parker had his moments, landing some telling individual punches in a contest where the approaches failed to mesh, with excessive holding disrupting the contest.
The scoring judges had it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my greatest display but what do champions do? They prevail," the victor stated in the ring as he was faced boos from the audience.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers believed the challenger, 31, merited the victory but the contender suffered the second setback of his 28-bout career.
Buatsi Claims Triumph in Uneventful Affair
Buatsi's progress has plateaued in recent times through management issues and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now stands trying to achieve expectations - perhaps in what appears to be a last chance - under new promotional backing.
He started carefully, with the two boxers prepared to take risks in a tentative opening few rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in 2022 after breaking his hand during the bout, was participating in his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who utilized a tight guard to edge the cleaner periods.
The crowd's patience diminished because of regular grabbing, with the challenger going down various instances during grappling.
The underdog closed well, but several stanzas were difficult to score. However, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the likes of heavy hitter Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Arthur beat Bradley Rea by divided decision in a excellent local rivalry contest to win the European light heavyweight belt.
The venue grew hushed for a extremely emotional homage before the fight as 10 bells rang in honor of local hero Hatton, who died aged 46 in recently.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound faded, the quiet gave way to a shout of "there's just one Hatton".
The competition within the ring reflected the emotion. The eventual winner was sent to the canvas by a left hook directly to the face in the second round, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red attire of Arthur soon pressed ahead again. Across the ring, the opponent - in opposing blue - was damaged soon, heavy swelling forming under his orbital area as the pair landed hard punches.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with effective uppercuts as the intensity seldom decreased over twelve rounds.
The victor barely secured the verdict with scoring tallies of draw, 115-113 and clearer margin, but each competitor were determined and full of heart, all the qualities their idol Hatton represented.
