British light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a tight ten-round contest at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a fight where the techniques failed to mesh, with excessive holding spoiling the fight.
The officials had it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my greatest display but what do champions do? They win," the victor said in the ringside as he was faced boos from the audience.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers felt the challenger, thirty-one, merited the victory but the British boxer endured the second loss of his 28-fight career.
Buatsi Secures Victory in Dull Encounter
Buatsi's progress has slowed in recent times through contract problems and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now stands trying to achieve expectations - maybe in what appears to be a last chance - under recent support.
He started carefully, with both competitors ready to overcommit in a calculated initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was participating in his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who operated with a tight guard to edge the better stanzas.
The audience's tolerance wore thin because of regular grabbing, with Parker falling to the floor several times during grappling.
Parker closed well, but multiple periods were challenging to assess. Although, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the likes of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a outstanding local rivalry battle to win the European light heavyweight championship.
The arena fell silent for a deeply poignant homage ahead of the contest as 10 bells tolled in memory of local hero Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the location since the passing of Hatton. As the last bell faded, the quiet gave way to a chant of "there's only one Ricky Hatton".
The action during the bout matched the emotion. Arthur was floored by a powerful punch squarely on the jaw in the initial stage, standing uncertainly to his position on the count of eight.
But the Manchester United-red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up early, heavy swelling forming under his eye as the pair traded powerful shots.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur barely secured the result with official scores of 114-114, close margin and clearer margin, but each competitor were persistent and courageous, all the qualities their idol Hatton embodied.
