British light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a majority decision in a competitive 10-round contest at the boxing arena.
But Parker found success, landing some telling single shots in a contest where the approaches didn't complement each other, with constant grabbing marring the contest.
Two judges scored it 96-94 for to the winner, with the final judge a even score.
"It wasn't my greatest display but what defines champions? They prevail," Buatsi commented in the ringside as he was faced negative reactions from the crowd.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Various analysts believed the challenger, thirty-one, should have been awarded the decision but the British boxer endured the second defeat of his 28-fight career.
Buatsi Secures Win in Dull Affair
The fighter's advancement has slowed in recent years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers ready to overcommit in a tentative initial rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after suffering a hand injury during the bout, was participating in his second bout at light heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for the favorite, who worked behind a tight guard to edge the better rounds.
The crowd's patience diminished amid constant clinching, with the challenger going down several times during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels All-Manchester Contest
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a excellent Manchester vs Manchester contest to secure the continental title.
The arena grew hushed for a extremely emotional homage ahead of the contest as a bell ceremony tolled in remembrance of local hero Hatton, who succumbed at age 46 in September.
It was the first major televised fight night in the location since the passing of Hatton. As the concluding sound ended, the silence transitioned to a shout of "there's just one Ricky Hatton".
The fighting within the ring equaled the emotion. Arthur was sent to the canvas by a significant blow squarely on the jaw in the second round, rising shakily to his footing on the count of eight.
But the red-colored attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was injured quickly, significant bruising appearing under his eye as the duo exchanged hard punches.
Rea, 27, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace seldom decreased over 12 rounds.
The victor narrowly won the result with official scores of even score, narrow lead and clearer margin, but both fighters were persistent and courageous, everything their inspiration the legend embodied.
