UK light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But the challenger had his moments, landing some telling single shots in a contest where the styles didn't complement each other, with excessive holding marring the action.
Two judges had it 96-94 to the winner, with the remaining official a even score.
"It wasn't my greatest display but what defines champions? They succeed," the victor stated in the arena as he was met by disapproval from the audience.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Some ringside observers thought the challenger, 31, merited the win but the Derbyshire fighter suffered the second setback of his 28-fight professional journey.
Buatsi Secures Triumph in Uneventful Match
The fighter's advancement has stalled in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers prepared to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who operated with a tight guard to narrowly win the cleaner periods.
The spectators' acceptance wore thin amid constant clinching, with Parker slipping to the canvas several times during grappling.
Parker finished the stronger, but multiple periods were difficult to score. However, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Hatton Memorial Fuels All-Manchester Fight
In the supporting bout, Arthur beat Rea by split-decision in a outstanding all-Manchester fight to secure the European light heavyweight championship.
The arena grew hushed for a profoundly moving memorial ahead of the contest as 10 bells tolled in memory of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the first major televised match card in the urban center since Hatton's passing. As the concluding sound disappeared, the quiet transitioned to a chant of "only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. Arthur was knocked down by a powerful punch flush on the chin in the second round, rising shakily to his feet on the count of eight.
But the traditional red equipment of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was damaged soon, noticeable damage developing under his eye as the fighters exchanged powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the intensity seldom decreased over 12 rounds.
The victor narrowly won the decision with official scores of draw, narrow lead and clearer margin, but the two athletes were persistent and brave, everything their idol the legend stood for.
