UK light-heavyweight Joshua Buatsi earned a win yet underwhelming beginning to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close ten-round fight at the boxing arena.
But the challenger found success, delivering effective single shots in a contest where the styles never quite clicked, with constant grabbing marring the contest.
The scoring judges had it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi said in the ring as he was greeted with negative reactions from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Some ringside observers believed the challenger, thirty-one, merited the win but the British boxer endured the second setback of his 28-match professional journey.
Buatsi Claims Victory in Uneventful Match
His career development has stalled in recent years through contract problems and long spells of lack of fights.
Once tipped as the next star of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under recent support.
He started carefully, with both competitors willing to take risks in a tentative early stages.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a protective stance to narrowly win the better periods.
The spectators' acceptance decreased amid frequent holding, with Parker going down several times during grappling.
Parker ended stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Motivates All-Manchester Battle
In the supporting bout, Arthur overcame Rea by close verdict in a terrific all-Manchester contest to secure the European light heavyweight belt.
The arena fell silent for a deeply poignant tribute before the fight as ten bells tolled in remembrance of local hero Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast boxing event in the location since the passing of Hatton. As the final chime disappeared, the stillness became a shout of "there's only one Hatton".
The action during the bout matched the sentiment. Arthur was knocked down by a left hook flush on the face in the early round, getting up unsteadily to his footing on the referee's count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was injured soon, noticeable damage developing under his eye as the pair exchanged powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the intensity rarely dropped over the full distance.
The victor edged the verdict with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were relentless and brave, exactly what their hero the legend stood for.
