British light heavyweight Joshua Buatsi secured a victory yet disappointing start to his career under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a tight ten-round bout at the Manchester venue.
But the challenger had his moments, landing some telling single shots in a match where the techniques didn't complement each other, with frequent clinching marring the action.
The officials judged it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my greatest showing but what do champions do? They prevail," Buatsi stated in the ringside as he was met by negative reactions from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Some ringside observers thought the challenger, thirty-one, deserved the decision but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
Buatsi Claims Triumph in Slow Encounter
His career development has stalled in the past few years through management issues and extended periods of lack of fights.
Previously predicted as the next star of British boxing, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter ready to take risks in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who operated with a protective stance to edge the better periods.
The spectators' acceptance decreased amid regular grabbing, with the challenger slipping to the canvas various instances during grappling.
Parker finished the stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just one round.
The victor moves on, but with the presence of hard hitter David Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Hatton Tribute Motivates Local Rivalry Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a excellent Manchester vs Manchester battle to win the European light-heavyweight belt.
The venue became quiet for a deeply poignant memorial before the fight as a bell ceremony sounded in memory of the city's native Hatton, who succumbed at age 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the concluding sound disappeared, the silence transitioned to a chant of "only one Ricky Hatton".
The competition inside the ropes reflected the emotion. The eventual winner was sent to the canvas by a left hook squarely on the face in the second round, standing uncertainly to his feet on the count of eight.
But the Manchester United-red equipment of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was injured early, heavy swelling forming under his orbital area as the fighters exchanged punishing blows.
Rea, 27, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over the full distance.
Arthur barely secured the result with judges scorecards of draw, 115-113 and clearer margin, but each competitor were determined and courageous, everything their idol Hatton represented.
