UK light-heavyweight Joshua Buatsi secured a victory yet unimpressive start to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a majority decision in a tight 10-round fight at the boxing arena.
But the challenger had his moments, landing some telling individual punches in a fight where the approaches didn't complement each other, with constant grabbing disrupting the contest.
The scoring judges scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi stated in the ringside as he was greeted with negative reactions from the audience.
The Londoner bounced back after his initial pro loss - an thrilling contest with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers thought Parker, 31, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-fight career.
Buatsi Secures Win in Uneventful Encounter
Buatsi's progress has slowed in recent times through contract problems and considerable time of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to fulfil that early promise - possibly in what feels like a final roll of the dice - under fresh management.
He started carefully, with neither fighter willing to be aggressive in a cagey early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to narrowly win the better periods.
The crowd's patience decreased during frequent holding, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog closed well, but many rounds were challenging to assess. Nevertheless, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi advances, but with the likes of hard hitter David Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Motivates All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent all-Manchester battle to secure the continental championship.
The venue fell silent for a profoundly moving homage before the fight as 10 bells sounded in honor of Manchester's own Hatton, who died at age 46 in last month.
It was the premier televised match card in the city since the passing of Hatton. As the last bell faded, the silence became a shout of "there's only one Ricky Hatton".
The action during the bout matched the feeling. The eventual winner was floored by a left hook directly to the face in the initial stage, rising shakily to his position on the count of eight.
But the Manchester United-red attire of Arthur soon pressed ahead again. On the opposite side, Rea - in competitive blue - was injured early, significant bruising developing under his face as the duo exchanged hard punches.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the action seldom decreased over twelve rounds.
The victor edged the decision with judges scorecards of even score, narrow lead and clearer margin, but each competitor were persistent and brave, everything their hero the legend represented.
