UK light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a close 10-round fight at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the styles failed to mesh, with frequent clinching disrupting the contest.
Two judges scored it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi commented in the arena as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers thought Parker, 31, deserved the victory but the British boxer endured the second setback of his 28-match professional journey.
Buatsi Earns Victory in Uneventful Encounter
Buatsi's progress has plateaued in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now stands trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He opened tentatively, with the two boxers ready to be aggressive in a calculated initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who operated with a tight guard to barely take the better rounds.
The spectators' acceptance decreased during regular grabbing, with Parker falling to the floor various instances during close exchanges.
The underdog ended stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent local rivalry battle to secure the European light heavyweight championship.
The venue grew hushed for a profoundly moving homage prior to the bout as ten bells tolled in remembrance of the city's native Hatton, who succumbed aged 46 in recently.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the last bell ended, the silence became a roar of "there's only one Hatton".
The action within the ring reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the jaw in the second round, getting up unsteadily to his feet on the count of eight.
But the red-colored shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was damaged quickly, noticeable damage developing under his orbital area as the duo landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace rarely dropped over 12 rounds.
Arthur barely secured the result with scoring tallies of 114-114, narrow lead and clearer margin, but each competitor were determined and courageous, exactly what their idol Hatton stood for.
