UK light heavyweight Joshua Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a close ten-round fight at the boxing arena.
But the challenger found success, connecting with powerful clean blows in a fight where the techniques never quite clicked, with frequent clinching marring the contest.
The officials had it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but how do champions respond? They win," Buatsi commented in the arena as he was greeted with boos from the audience.
The British fighter got back to winning after his maiden career setback - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Some ringside observers believed Parker, 31, merited the win but the British boxer experienced the second loss of his 28-match professional journey.
Buatsi Earns Win in Slow Match
His career development has stalled in recent years through contract problems and long spells of inactivity.
Previously predicted as the next star of the British fight scene, he now is positioned trying to realize his potential - perhaps in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors prepared to be aggressive in a tentative opening few rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second bout at light heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who utilized a tight guard to barely take the cleaner stanzas.
The spectators' acceptance diminished during constant clinching, with Parker going down various instances during clinches.
The underdog closed well, but many rounds were challenging to assess. However, former world champion the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires All-Manchester Contest
In the secondary fight, Arthur defeated Rea by divided decision in a outstanding all-Manchester fight to win the European light heavyweight belt.
The venue fell silent for a extremely emotional memorial before the fight as 10 bells tolled in remembrance of local hero Ricky Hatton, who died aged 46 in last month.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the final chime faded, the silence became a shout of "there's only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. Arthur was knocked down by a left hook flush on the jaw in the second round, standing uncertainly to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged early, significant bruising developing under his eye as the duo exchanged powerful shots.
Rea, 27, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the pace seldom decreased over the full distance.
Arthur edged the decision with scoring tallies of 114-114, 115-113 and wider gap, but the two athletes were persistent and courageous, everything their hero the legend embodied.
