British light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a competitive 10-round bout at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective individual punches in a match where the techniques didn't complement each other, with constant grabbing disrupting the fight.
The scoring judges judged it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my greatest performance but what defines champions? They prevail," Buatsi commented in the ringside as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Several boxing experts felt Parker, 31, deserved the win but the contender endured the second loss of his 28-bout career.
Buatsi Earns Triumph in Dull Encounter
Buatsi's progress has stalled in the past few years through management issues and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under recent support.
He began cautiously, with the two boxers prepared to take risks in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after suffering a hand injury during the bout, was competing in only his second fight at light heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for the favorite, who worked behind a solid defense to narrowly win the better periods.
The audience's tolerance decreased amid regular grabbing, with the challenger slipping to the canvas several times during grappling.
The underdog ended stronger, but multiple periods were hard to judge. However, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for Parker, giving Buatsi just one round.
The victor advances, but with the likes of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Arthur defeated Rea by split-decision in a excellent local rivalry contest to win the European light heavyweight title.
The stadium fell silent for a extremely emotional homage ahead of the contest as 10 bells tolled in honor of the city's native Hatton, who passed away 46 years old in recently.
It was the initial significant broadcast match card in the city since Hatton's passing. As the concluding sound faded, the stillness became a chant of "there's just one Ricky Hatton".
The fighting during the bout matched the emotion. Arthur was knocked down by a powerful punch squarely on the chin in the early round, standing uncertainly to his footing on the referee's count.
But the red-colored shorts of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was damaged quickly, significant bruising forming under his eye as the duo exchanged hard punches.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the pace seldom decreased over twelve rounds.
The victor narrowly won the verdict with official scores of 114-114, close margin and clearer margin, but the two athletes were persistent and courageous, all the qualities their inspiration the legend stood for.
