British light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a competitive ten-round bout at the Manchester venue.
But Parker found success, delivering effective individual punches in a contest where the techniques failed to mesh, with excessive holding spoiling the action.
The officials scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best showing but how do champions respond? They prevail," the victor commented in the arena as he was greeted with disapproval from the spectators.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter endured the second defeat of his 28-bout professional journey.
The Champion Secures Triumph in Uneventful Affair
His career development has slowed in the past few years through contract problems and long spells of inactivity.
Previously predicted as the future of British boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a final roll of the dice - under fresh management.
He started carefully, with both competitors ready to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had kept it close, causing problems for the favorite, who operated with a protective stance to barely take the more effective stanzas.
The audience's tolerance wore thin amid regular grabbing, with Parker going down several times during grappling.
The underdog ended stronger, but several stanzas were difficult to score. However, ex-champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor progresses, but with the likes of power puncher Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Fuels All-Manchester Contest
In the secondary fight, Arthur beat Rea by close verdict in a outstanding all-Manchester fight to win the European light heavyweight belt.
The stadium fell silent for a deeply poignant tribute before the fight as a bell ceremony rang in honor of Manchester's own Ricky Hatton, who succumbed at age 46 in September.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime disappeared, the stillness gave way to a shout of "there's just one Hatton".
The action during the bout equaled the feeling. Arthur was knocked down by a significant blow directly to the face in the initial stage, rising shakily to his position on the count of eight.
But the Manchester United-red equipment of the fighter soon came forward again. Across the ring, the opponent - in rival City blue - was injured soon, noticeable damage appearing under his face as the fighters exchanged punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur narrowly won the result with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were determined and brave, everything their inspiration the legend stood for.
