UK light-heavyweight Joshua Buatsi made a winning yet unimpressive beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a majority decision in a competitive ten-round contest at the boxing arena.
But Parker had his moments, landing some telling clean blows in a fight where the techniques didn't complement each other, with excessive holding marring the fight.
Two judges had it 96-94 to the winner, with the third a 95-95.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi said in the ringside as he was faced negative reactions from the audience.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Various analysts felt Parker, thirty-one, merited the victory but the contender endured the second loss of his 28-bout career.
Buatsi Earns Triumph in Slow Encounter
Buatsi's progress has plateaued in the past few years through management issues and long spells of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to realize his potential - possibly in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to take risks in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand during the bout, was making just his second bout at light heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance decreased during regular grabbing, with the challenger going down several times during close exchanges.
The underdog closed well, but several stanzas were challenging to assess. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a excellent local rivalry contest to secure the continental title.
The stadium fell silent for a profoundly moving tribute before the fight as a bell ceremony sounded in honor of local hero Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast match card in the city since Hatton's death. As the last bell faded, the quiet transitioned to a chant of "there's just one Ricky Hatton".
The fighting during the bout equaled the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the face in the second round, rising shakily to his position on the eight count.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was damaged quickly, heavy swelling forming under his face as the pair traded powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with powerful upward punches as the pace hardly diminished over the full distance.
Arthur barely secured the verdict with scoring tallies of draw, 115-113 and wider gap, but the two athletes were persistent and brave, exactly what their hero the legend represented.
