British light heavyweight Joshua Buatsi made a winning yet unimpressive start to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a tight ten-round fight at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a contest where the techniques failed to mesh, with constant grabbing spoiling the contest.
Two judges had it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor commented in the ringside as he was greeted with negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in February - to claim a twentieth professional win.
Various analysts thought Parker, 31, should have been awarded the victory but the British boxer experienced the second loss of his 28-match career.
Buatsi Claims Win in Dull Affair
His career development has plateaued in recent years through promotional disputes and extended periods of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to realize his potential - maybe in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter prepared to be aggressive in a calculated initial rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to edge the cleaner rounds.
The spectators' acceptance wore thin because of frequent holding, with Parker slipping to the canvas various instances during grappling.
Parker ended stronger, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the likes of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Hatton Homage Motivates All-Manchester Battle
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a outstanding all-Manchester battle to secure the European light-heavyweight title.
The stadium fell silent for a extremely emotional homage prior to the bout as 10 bells tolled in honor of local hero Ricky Hatton, who passed away at age 46 in recently.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the concluding sound faded, the silence gave way to a shout of "only one Hatton".
The action during the bout matched the emotion. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the second round, rising shakily to his position on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up early, heavy swelling developing under his face as the pair exchanged hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the pace seldom decreased over twelve rounds.
The victor narrowly won the result with judges scorecards of even score, narrow lead and wider gap, but each competitor were persistent and brave, everything their inspiration Hatton represented.
